Report
of
the
NOAA
Panel
on
Contingent
Valuation
January
11,
1993
Kenneth
Arrow
Robert
Solow
Paul
R.
Portney
Edward
E.
Leamer
Roy
Radner
Howard
Schuman
Report
of
the
NOAA
Panel
on
Contingent
Valuation
Date:
May
9,
2001
I.
INTRODUCTION
Under
the
Oil
Pollution
Act
of
1990,
the
President­­
acting
through
the
Under
Secretary
of
Commerce
for
Oceans
and
Atmosphere­­
is
required
to
issue
regulations
establishing
procedures
for
assessing
damages
to
or
destruction
of
natural
resources
resulting
from
a
discharge
of
oil
covered
by
the
Act.

These
procedures
are
to
ensure
the
recovery
of
restoration
costs
as
well
as
the
diminution
in
value
of
the
affected
resources
and
any
reasonable
costs
of
conducting
the
damage
assessment.

At
least
some
of
the
values
that
might
be
diminished
by
such
a
discharge
are
relatively
straightforward
to
measure
through
information
revealed
in
market
transactions.
For
instance,
if
the
discharge
kills
fish
and
thereby
reduces
the
incomes
of
commercial
fishermen,
their
losses
can
reasonably
be
calculated
by
the
reduced
catch
multiplied
by
the
market
price(
s)
of
the
fish
(
less,
of
course,
any
costs
they
would
have
incurred).

Similarly,
if
the
discharge
of
oil
discourages
tourist
travel
to
an
area,
the
lost
incomes
of
those
owning
and/
or
operating
motels,
cottages,
or
other
facilities
can
be
reasonably
represented
by
the
difference
in
revenues
between
the
affected
period
and
a
"
normal"
season.
Even
the
losses
to
recreational
fishermen,
boaters,
swimmers,
hikers,
and
others
who
make
active
use
of
the
areas
affected
by
the
discharge
can
be
included
in
the
estimate
of
diminished
value,
although
these
losses
will
2
generally
be
somewhat
more
difficult
to
value
than
the
more
obvious
out­
of­
pocket
losses.

The
losses
described
above
have
come
to
be
known
as
lost
"
use
values"
because
they
are
experienced
by
those
who,
in
a
variety
of
different
ways,
make
active
use
of
the
resources
adversely
affected
by
the
discharge.
But
for
at
least
the
last
twenty­
five
years,
economists
have
recognized
the
possibility
that
individuals
who
make
no
active
use
of
a
particular
beach,

river,
bay,
or
other
such
natural
resource
might,
nevertheless,

derive
satisfaction
from
its
mere
existence,
even
if
they
never
intend
to
make
active
use
of
it.

This
concept
has
come
to
be
known
as
"
existence
value"
and
it
is
the
major
element
of
what
are
now
referred
to
as
"
non­
use"

or
"
passive­
use"
values
(
the
latter
term
is
employed
in
the
balance
of
this
report).
In
regulations
promulgated
by
the
Department
of
the
Interior
in
1986
under
the
Comprehensive
Environmental
Response,
Compensation,
and
Liability
Act
­­

regulations
that
also
pertained
to
natural
resource
damage
assessments
­­
passive­
use
values
were
included
among
the
losses
for
which
trustees
could
recover.
The
inclusion
of
passive­
use
values
was
recently
upheld
by
the
D.
C.
Court
of
Appeals
(
State
of
Ohio
v.
Department
of
the
Interior,
880
F.
2d
432
(
D.
C.
Cir.

1989)),
as
long
as
they
could
be
reliably
measured.

This
begs
an
interesting
and
important
question,
however.

If
passive­
use
values
are
to
be
included
among
the
compensable
losses
for
which
trustees
can
make
recovery
under
the
Oil
3
Pollution
Act,
how
will
they
be
estimated?
Unlike
losses
to
commercial
fishermen
or
recreational
property
owners,
there
are
no
direct
market
transactions
that
can
be
observed
to
provide
information
on
which
estimates
can
be
based.
Unlike
losses
to
boaters,
swimmers,
recreational
fishermen
and
others,
there
exist
no
indirect
methods
through
which
market
data
can
provide
at
least
some
clues
as
to
lost
values.
In
other
words,
there
appear
to
be
neither
obvious
nor
even
subtle
behavioral
trails
that
can
provide
information
about
lost
passive­
use
values.

Some
experts
believe
that
there
exists
an
approach
that
can
provide
useful
information
about
the
economic
significance
of
the
lost
passive­
use
values
individuals
may
suffer
when
oil
discharges
damage
natural
resources.
Known
as
the
contingent
valuation
(
or
CV)
technique,
this
approach
is
based
on
the
direct
elicitation
of
these
values
from
individuals
through
the
use
of
carefully
designed
and
administered
sample
surveys.
Its
appeal
lies
in
its
potential
to
inform
damage
assessment
in
an
area
(
lost
passive­
use
values)
where
there
appear
to
be
no
behavioral
trails
to
be
followed.

Typically,
CV
studies
provide
respondents
with
information
about
a
hypothetical
government
program
that
would
reduce
the
likelihood
of
a
future
adverse
environmental
event
such
as
an
oil
spill,
chemical
accident,
or
the
like.
Respondents
are
usually
given
some
specific
information
about
the
exact
nature
of
the
damages
that
the
program
in
question
would
prevent.
And
they
are
also
confronted
in
the
study
with
a
question
or
questions
that
4
provide
information
about
the
economic
sacrifice
they
would
have
to
make
to
support
the
environmental
program.
This
may
take
the
form
of
an
open­
ended
question
asking
what
is
the
maximum
amount
they
would
be
willing
to
pay
for
the
program
in
question;
it
may
involve
a
series
of
questions
confronting
them
with
different
prices
for
the
program
depending
on
their
previous
answers;
or
it
may
take
the
form
of
a
hypothetical
referendum
(
like
a
school
bond
issue)
in
which
respondents
are
told
how
much
each
would
have
to
pay
if
the
measure
passed
and
are
then
asked
to
cast
a
simple
"
yes"
or
"
no"
vote.
(
The
conceptually
correct
measure
of
lost
passive­
use
value
for
environmental
damage
that
has
already
occurred
is
the
minimum
amount
of
compensation
that
each
affected
individual
would
be
willing
to
accept.
Nevertheless,
because
of
concern
that
respondents
would
give
unrealistically
high
answers
to
such
questions,
virtually
all
previous
CV
studies
have
described
scenarios
in
which
respondents
are
asked
to
pay
to
prevent
future
occurrences
of
similar
accidents.
This
is
the
conservative
choice
because
willingness
to
accept
compensation
should
exceed
willingness
to
pay,
if
only
trivially;
we
say
more
about
other
biases
below.)

The
CV
technique
has
been
used
for
twenty
years
or
so
to
estimate
passive­
use
values.
In
the
last
five
years,
however,

there
has
been
a
dramatic
increase
in
the
number
of
academic
papers
and
presentations
related
to
the
CV
technique.
This
is
due
in
part
to
the
availability
of
comprehensive
reference
texts
on
the
subject
(
Mitchell
and
Carson
(
1989),
for
instance),
and
to
5
the
growing
interest
both
nationally
and
internationally
in
environmental
problems
and
policies.
But
it
is
also
attributable
to
the
growing
use
of
the
CV
technique
in
estimating
lost
passive­
use
values
in
litigation
arising
from
state
and
federal
statutes
designed
to
protect
natural
resources.
Since
Ohio
v.

Department
of
the
Interior
admitted
the
concept
of
passive­
use
values
in
damage
assessments,
this
can
only
give
added
impetus
to
the
use
of
CV
in
such
litigation.

The
CV
technique
is
the
subject
of
great
controversy.
Its
detractors
argue
that
respondents
give
answers
that
are
inconsistent
with
the
tenets
of
rational
choice,
that
these
respondents
do
not
understand
what
it
is
they
are
being
asked
to
value
(
and,
thus,
that
stated
values
reflect
more
than
that
which
they
are
being
asked
to
value),
that
respondents
fail
to
take
CV
questions
seriously
because
the
results
of
the
surveys
are
not
binding,
and
raise
other
objections
as
well.
Proponents
of
the
CV
technique
acknowledge
that
its
early
(
and
even
some
current)

applications
suffered
from
many
of
the
problems
critics
have
noted,
but
believe
that
more
recent
and
comprehensive
studies
have
already
or
soon
will
be
able
to
deal
with
these
objections.

This
(
sometimes
acrimonious)
debate
has
put
the
National
Oceanic
and
Atmospheric
Administration
(
NOAA)
in
a
very
difficult
spot.
NOAA
must
decide
in
promulgating
the
regulations
under
the
Oil
Pollution
Act
whether
the
CV
technique
is
capable
of
providing
reliable
information
about
lost
existence
or
other
passive­
use
values.
Toward
this
end,
NOAA
appointed
the
6
Contingent
Valuation
Panel
to
consider
this
question
and
make
recommendations
to
it.

This
report
is
the
product
of
the
Panel's
deliberations
and
is
organized
in
the
following
way.
Following
this
introduction,
the
drawbacks
to
the
CV
technique
are
discussed
in
Section
II.
Section
III
discusses
several
key
issues
concerning
the
design
of
CV
surveys,
including
use
of
the
referendum
format
to
elicit
individual
values,
ways
of
addressing
the
so­
called
"
embedding"
problem,
and
the
evaluation
of
damages
that
last
for
some
period
but
not
forever.
Section
IV
presents
guidelines
to
which
the
Panel
believes
any
CV
study
should
adhere
if
the
study
is
to
produce
information
useful
in
natural
resource
damage
assessment.
(
These
are
elaborated
upon
in
an
Appendix.)
In
Section
V
a
research
agenda
is
described;
it
is
the
Panel's
belief
that
future
applications
of
the
CV
technique
may
be
less
time­
consuming
and
contentious
if
the
research
described
in
the
agenda
is
carried
out.
Section
VI
presents
the
Panel's
conclusions.

II.
CRITICISMS
OF
THE
CONTINGENT
VALUATION
METHOD
The
contingent
valuation
method
has
been
criticized
for
many
reasons
and
the
Panel
believes
that
a
number
of
these
criticisms
are
particularly
compelling.
Before
identifying
and
discussing
these
problems,
however,
it
is
worth
pointing
out
that
they
all
take
on
added
importance
in
light
of
the
impossibility
of
validating
externally
the
results
of
CV
studies.
It
should
be
7
noticed,
however,
that
this
same
disadvantage
must
inhere
in
any
method
of
assessing
damages
from
deprivation
of
passive­
use.
It
is
not
special
to
the
CV
approach
although,
as
suggested
in
Section
I,
there
are
currently
no
other
methods
capable
of
providing
information
on
these
values.

One
way
to
evade
this
difficulty,
at
least
partially,
is
to
construct
experiments
in
which
an
artificial
opportunity
is
created
to
pay
for
environmental
goods.
The
goods
in
question
can
perfectly
well
involve
passive
use.
Then
the
results
of
a
CV
estimate
of
willingness
to
pay
can
be
compared
with
the
"
real"

results
when
the
opportunity
is
made
available
to
the
same
sample
or
an
analogous
sample.

A
few
such
experiments
have
been
attempted.
The
most
recent,
due
to
Seip
and
Strand
(
1992),
used
CV
to
estimate
willingness
to
pay
for
membership
in
a
Norwegian
organization
devoted
to
environmental
affairs,
and
compared
this
estimate
with
actual
responses
when
a
number
of
the
same
respondents
were
presented
with
an
opportunity
actually
to
contribute.
The
finding
was
that
self­
reported
willingness
to
pay
was
significantly
greater
than
"
actual"
willingness
to
pay.
A
recent
study
by
Duffield
and
Patterson
(
1991)
took
as
the
environmental
amenity
in
question
the
maintenance
of
stream
flow
in
two
Montana
rivers.
The
rivers
in
question
provided
spawning
grounds
for
two
rare
species
of
fish;
passive
use
was
believed
to
be
the
main
motivation
for
respondents.
One
of
two
parallel
samples
was
asked
about
hypothetical
willingness
to
contribute
to
the
Montana
8
Nature
Conservancy
which
would
then
maintain
stream
flow;
the
other
was
offered
an
opportunity
actually
to
contribute
to
the
same
organization
for
the
same
purpose.
It
was
found
that
response
rates
and
expressed
willingness
to
contribute
were
significantly
higher
when
the
contribution
was
hypothetical
than
when
"
expressed
willingness"
meant
an
immediate
cash
contribution.
On
the
other
hand,
the
size
of
contributions,

hypothetical
in
one
case
and
actual
in
the
other,
was
not
much
different
as
between
those
who
said
they
would
contribute
and
those
who
did
so.

These
studies
suggest
that
the
CV
technique
is
likely
to
overstate
"
real"
willingness
to
pay.
Duffield
and
Patterson,

however,
hold
out
hope
that
the
differences
are
small
enough
and
predictable
enough
that
CV
estimates
could
be
discounted
for
possible
overstatement
and
then
used
as
a
conservative
estimate
of
willingness
to
pay.
Clearly
more
such
experiments
would
be
useful.

A
less
direct
test
of
the
"
reality"
of
CV
estimates
of
lost
passive
use
values
is
to
use
the
technique
to
estimate
willingness
to
pay
for
ordinary
market
goods
and
then
to
compare
the
results
with
actual
purchases.
This
has
been
tried
by
Dickie,
Fisher,
and
Gerking
(
1987)
using
the
demand
for
strawberries.
When
the
data
were
re­
analyzed
by
Diamond,

Hausman,
Leonard,
and
Denning
(
1992),
it
was
found
that
the
CV
approach
tended
systematically
to
overestimate
quantity
demanded
at
each
price,
sometimes
by
as
much
as
50
percent.
This
result
9
has
to
be
qualified
in
two
ways.
First,
the
original
CV
study
seems
to
have
been
fairly
casual
by
the
standards
now
proposed
by
practitioners;
pre­
testing
and
improvement
of
the
survey
instrument
might
(
perhaps)
have
narrowed
the
gap.
And
second,
it
seems
to
go
too
far
to
conclude
from
systematic
over­
estimation
that
the
CV
study,
even
as
conducted,
provides
no
information
about
the
demand
for
strawberries.
Much
of
the
same
could
be
said
about
a
study
submitted
to
the
Panel
by
Cummings
and
Harrison
(
1992)
comparing
hypothetical
and
demonstrated
willingness
to
pay
for
small
household
goods.
(
See
also
Bishop
and
Heberlein
(
1979).)

External
validation
of
the
CV
method
remains
an
important
issue.
A
critically
important
contribution
could
come
from
experiments
in
which
state­
of­
the­
art
CV
studies
are
employed
in
contexts
where
they
can
in
fact
be
compared
with
"
real"

behavioral
willingness
to
pay
for
goods
that
can
actually
be
bought
and
sold.

Of
the
other
problems
arising
in
CV
studies,
the
following
are
of
most
concern
to
the
Panel:
(
i)
the
contingent
valuation
method
can
produce
results
that
appear
to
be
inconsistent
with
assumptions
of
rational
choice;
(
ii)
responses
to
CV
surveys
sometimes
seem
implausibly
large
in
view
of
the
many
programs
for
which
individuals
might
be
asked
to
contribute
and
the
existence
of
both
public
and
private
goods
that
might
be
substitutes
for
the
resource(
s)
in
question;
(
iii)
relatively
few
previous
applications
of
the
CV
method
have
reminded
respondents
10
forcefully
of
the
budget
constraints
under
which
all
must
operate;
(
iv)
it
is
difficult
in
CV
surveys
to
provide
adequate
information
to
respondents
about
the
policy
or
program
for
which
values
are
being
elicited
and
to
be
sure
they
have
absorbed
and
accepted
this
information
as
the
basis
for
their
responses;

(
v)
in
generating
aggregate
estimates
using
the
CV
technique,
it
is
sometimes
difficult
determining
the
"
extent
of
the
market;"

and
(
vi)
respondents
in
CV
surveys
may
actually
be
expressing
feelings
about
public
spiritedness
or
the
"
warm
glow"
of
giving,

rather
than
actual
willingness
to
pay
for
the
program
in
question.
We
discuss
each
of
these
briefly.

Inconsistency
with
Rational
Choice
Some
of
the
empirical
results
produced
by
CV
studies
have
been
alleged
to
be
inconsistent
with
the
assumptions
of
rational
choice.
This
raises
two
questions:
What
requirements
are
imposed
by
rationality?
Why
are
they
relevant
to
the
evaluation
of
the
reliability
of
the
CV
method?

Rationality
in
its
weakest
form
requires
certain
kinds
of
consistency
among
choices
made
by
individuals.
For
instance,
if
an
individual
chooses
some
purchases
at
a
given
set
of
prices
and
income,
then
if
some
prices
fall
and
there
are
no
other
changes,

the
goods
that
the
individual
would
now
buy
would
make
him
or
her
better
off.
Similarly,
we
would
expect
an
individual's
preferences
over
public
goods
(
i.
e.,
bridges,
highways,
air
quality)
to
reflect
the
same
kind
of
consistency.
11
Common
notions
of
rationality
impose
other
requirements
which
are
relevant
in
different
contexts.
Usually,
though
not
always,
it
is
reasonable
to
suppose
that
more
of
something
regarded
as
good
is
better
so
long
as
an
individual
is
not
satiated.
This
is
in
general
translated
into
a
willingness
to
pay
somewhat
more
for
more
of
a
good,
as
judged
by
the
individual.
Also,
if
marginal
or
incremental
willingness
to
pay
for
additional
amounts
does
decline
with
the
amount
already
available,
it
is
usually
not
reasonable
to
assume
that
it
declines
very
abruptly.

This
point
assumes
importance
in
view
of
some
empirical
evidence
from
CV
studies
that
willingness
to
pay
does
not
increase
with
the
good.
In
one
study,
Kahneman
(
1986)
found
that
willingness
to
pay
for
the
cleanup
of
all
lakes
in
Ontario
was
only
slightly
more
than
willingness
to
pay
for
cleaning
up
lakes
in
just
one
region.
Evidence
of
this
kind
has
multiplied
(
see
Kahneman
and
Knetch
(
1992),
Desvousges,
et
al.
(
1992),
and
Diamond
et
al.
(
1992)).
Desvousges'
result
is
very
striking;
the
average
willingness
to
pay
to
take
measures
to
prevent
2,000
migratory
birds
(
not
endangered
species)
from
dying
in
oil­
filled
ponds
was
as
great
as
that
for
preventing
20,000
or
200,000
birds
from
dying.
Diminishing
marginal
willingness
to
pay
for
additional
protection
could
be
expected
to
result
in
some
drop.

But
a
drop
to
zero,
especially
when
the
willingness
to
pay
for
the
first
2,000
birds
is
certainly
not
trivial,
is
hard
to
explain
as
the
expression
of
a
consistent,
rational
set
of
12
choices.

It
has
been
argued
on
a
more
technical
level
that
the
studies
finding
such
apparent
inconsistencies
are
defective,
that
the
choices
are
not
presented
clearly
to
the
respondents.
In
the
study
referred
to
immediately
above,
for
instance,
respondents
were
told
that
2,000
birds
was
"...
much
less
than
1%"
of
the
total
migratory
bird
population
while
200,000
birds
was
"...
about
2%"
of
the
total.
This
may
have
led
respondents
to
evaluate
the
programs
as
being
essentially
the
same.
But
on
the
face
of
it,
the
evidence
certainly
raises
some
serious
questions
about
the
rationality
of
the
responses.

It
could
be
asked
whether
rationality
is
indeed
needed.
Why
not
take
the
values
found
as
given?
There
are
two
answers.
One
is
that
we
do
not
know
yet
how
to
reason
about
values
without
some
assumption
of
rationality,
if
indeed
it
is
possible
as
all.

Rationality
requirements
impose
a
constraint
on
the
possible
values,
without
which
damage
judgments
would
be
arbitrary.
A
second
answer
is
that,
as
discussed
above,
it
is
difficult
to
find
objective
counterparts
to
verify
the
values
obtained
in
response
to
questionnaires.
Therefore,
some
form
of
internal
consistency
is
the
least
we
would
need
to
feel
some
confidence
that
the
verbal
answers
corresponded
to
some
reality.

Implausibility
of
Responses
The
CV
method
is
generally
used
to
elicit
values
for
a
specific
program
to
prevent
environmental
damage,
whether
it
be
13
dead
animals,
spoilage
of
a
pristine
wilderness
area,
or
loss
of
visibility
in
some
very
unusually
clear
area.
Though
in
each
case,
individuals
often
express
zero
willingness
to
pay,
average
willingness
to
pay
over
the
whole
sample
is
often
at
least
a
few
dollars
and
frequently
$
20
to
$
50.
With
100,000,000
households
in
the
United
States,
these
responses
result
in
very
large
totals,
frequently
over
$
1
billion.
Some
have
argued
that
these
large
sums
are
in
themselves
incredible
and
cast
doubt
on
the
CV
method.
The
Panel
is
not
convinced
by
this
argument,
since
it
is
hard
to
have
an
intuition
as
to
a
reasonable
total.

But
there
is
a
different
problem
with
these
answers.
one
can
envision
many
possible
types
of
environmental
damage
­­
oil
spills
or
groundwater
contamination
in
many
different
locations,

visibility
impairment
in
a
variety
of
places,
and
so
on.
Would
the
average
individual
or
household
really
be
willing
to
pay
$
50
or
even
$
5
to
prevent
each
one?
This
seems
very
unlikely,
since
the
total
resulting
willingness
to
pay
for
all
such
programs
could
easily
become
a
very
large
fraction
of
one's
income
or
perhaps
even
exceed
it.

In
other
words,
even
if
the
willingness
to
pay
responses
to
individual
environmental
insults
are
correct
if
only
one
program
is
to
be
considered,
they
may
give
overestimates
when
there
are
expected
to
be
a
large
number
of
environmental
problems.

Similarly,
if
individuals
fail
to
consider
seriously
the
public
or
private
goods
that
might
be
substitutes
for
the
resources
in
question,
their
responses
to
questions
in
a
CV
survey
may
be
14
unrealistically
large.

Absence
of
a
Meaningful
Budget
Constraint
Even
if
respondents
in
CV
surveys
take
seriously
the
hypothetical
referendum
(
or
other
type
of)
questions
being
asked
them,
they
may
respond
without
thinking
carefully
about
how
much
disposable
income
they
have
available
to
allocate
to
all
causes,

public
and
private
(
see
Kemp
and
Maxwell
(
1992),
for
instance).

Specifically,
respondents
might
reveal
a
willingness
to
pay
of,

say,
$
100
for
a
project
that
would
reduce
the
risk
of
an
oil
spill;
but
if
asked
what
current
or
planned
expenditures
they
would
forgo
to
pay
for
the
program,
they
might
instead
re­
evaluate
their
responses
and
revise
them
downward.
This
is
similar
to
the
problem
identified
immediately
above
where
individuals
fail
to
think
of
the
possible
multiplicity
of
environmental
projects
or
policies
they
might
be
asked
to
support.
To
date,
relatively
few
CV
surveys
have
reminded
respondents
convincingly
of
the
very
real
economic
constraints
within
which
spending
decisions
must
be
made.

Information
Provision
and
Acceptance
If
CV
surveys
are
to
elicit
useful
information
about
willingness
to
pay,
respondents
must
understand
exactly
what
it
is
they
are
being
asked
to
value
(
or
vote
upon)
and
must
accept
the
scenario
in
formulating
their
responses.
Frequently,
CV
surveys
have
provided
only
sketchy
details
about
the
project(
s)
15
being
valued
and
this
calls
into
question
the
estimates
derived
therefrom.

Consider
the
following
example.
Suppose
information
is
desired
about
individuals'
willingness
to
pay
to
prevent
a
chemical
leak
into
a
river.
Presumably,
their
responses
would
depend
importantly
on
how
long
it
would
take
for
the
chemical
to
degrade
naturally
in
the
river
(
if
it
would
at
all),
what
ecological
and
human
health
damage
the
chemical
would
do
until
it
had
degraded,
and
so
on.
Absent
information
about
such
matters,

it
is
unreasonable
to
expect
even
very
bright
and
well­
informed
respondents
to
place
meaningful
values
on
a
program
to
prevent
leaks.

Even
if
detailed
information
were
supplied,
there
are
limits
on
the
ability
of
respondents
to
internalize
and
thus
accept
and
proceed
from
the
information
given.
It
is
one
thing
to
tell
respondents
matter­
of­
factly
that
complete
recovery
will
occur
in,
say,
two
years.
It
is
another
thing
for
them
to
accept
this
information
completely
and
then
incorporate
it
in
their
answers
to
difficult
questions.

To
return
to
the
example
above,
respondents
who
take
a
pessimistic
view
of
the
probable
consequences
of
a
chemical
leak
are
likely
to
report
relatively
high
willingness
to
pay
to
prevent
the
contamination
­­
too
high,
in
fact,
if
in
actuality
such
an
event
had
less
serious
effects.
On
the
other
hand,

respondents
with
an
exaggerated
sense
of
the
river's
assimilative
capacity
or
regenerative
power
could
be
expected
to
report
a
16
willingness
to
pay
that
understates
their
"
true"
valuation
if
provided
with
a
more
complete
description
of
likely
consequences.

To
repeat,
even
when
CV
surveys
provide
detailed
and
accurate
information
about
the
effects
of
the
program
being
valued,
respondents
must
accept
that
information
in
making
their
(
hypothetical)
choices.
If,
instead,
respondents
rely
on
a
set
of
heuristics
("
these
environmental
accidents
are
seldom
as
bad
as
we're
led
to
believe,"
or
"
authorities
almost
always
put
too
good
a
face
on
these
things"),
in
effect
they
will
be
answering
a
different
question
from
that
being
asked;
thus,
the
resulting
values
that
are
elicited
will
not
reliably
measure
willingness
to
pay.

Extent
of
the
Market
Suits
for
environmental
damages
are
brought
by
trustees
on
behalf
of
a
legally
definable
group.
This
group
limits
the
population
that
is
appropriate
for
determining
damages
even
though
individuals
outside
of
this
group
may
suffer
loss
of
passive
and
active
use.
Undersampling
and
even
zero
sampling
of
a
subgroup
of
the
relevant
population
may
be
appropriate
if
the
subgroup
has
a
predictably
low
valuation
of
the
resource.
For
example,
the
authors
of
the
CV
study
conducted
in
connection
with
the
Nestucca
oil
spill
limited
their
sample
to
households
in
Washington
and
British
Columbia
possibly
because
the
individuals
living
elsewhere
were
presumed
to
have
values
too
low
to
justify
examination
(
or
possibly
because
the
sponsors
of
the
study
were
17
agencies
of
the
State
of
washington
and
the
province
of
British
Columbia
and
so
defined
the
legally
appropriate
population)

(
Rowe,
Shaw,
and
Schulze,
1992).

"
Warm
Glow"
Effects
Some
critics
of
the
CV
technique
(
e.
g.,
Diamond
and
Hausman
(
1992))
have
observed
that
the
distribution
of
responses
to
open­
ended
questions
about
willingness
to
pay
often
is
characterized
by
a
significant
proportion
of
"
zeros"
­­
people
who
would
pay
nothing
for
the
program
­­
and
also
a
number
of
sizable
reports.
This
bi­
modal
distribution
also
characterizes
individual
giving:
most
of
us
give
nothing
to
most
charities,

but
give
non­
trivial
amounts
to
the
ones
we
do
support
(
at
least
$
10
or
$
20,
say).
This
has
led
these
critics
to
conclude
that
individuals'
responses
to
CV
questions
serve
the
same
function
as
charitable
contributions
­­
not
only
to
support
the
organization
in
question,
but
also
to
feel
the
"
warm
glow"
that
attends
donating
to
worthy
causes
(
see
Andreoni
(
1989)).
If
this
is
so,

CV
responses
should
not
be
taken
as
reliable
estimates
of
true
willingness
to
pay,
but
rather
as
indicative
of
approval
for
the
environmental
program
in
question.

III.
KEY
ISSUES
IN
THE
DESIGN
OF
CONTINGENT
VALUATION
INSTRUMENTS
In
the
course
of
its
deliberations,
the
Panel
discussed
many
issues
surrounding
the
design
of
CV
surveys.
Here
we
provide
our
18
views
on
several
issues
that
are
especially
important.
In
Section
IV
and
in
an
Appendix
to
this
report,
we
provide
much
greater
detail
on
the
characteristics
of
a
valid
application
of
the
CV
method.

The
Referendum
Format
Considered
as
a
survey,
a
CV
instrument
is
descriptive
rather
than
explanatory.
Description
may
be
as
simple
as
reporting
univariate
averages
of
one
kind
or
another,
such
as
the
percentages
of
those
employed,
seeking
work,
and
not
seeking
work
in
the
United
States,
the
mean
number
of
rooms
occupied
by
American
households,
or
the
proportion
of
"
likely"
voters
favoring
one
or
another
candidate
in
an
upcoming
election.
A
CV
study
seeks
to
find
the
average
willingness
to
pay
for
a
specific
environmental
improvement.
Nevertheless,
as
will
be
seen
later,

it
is
often
desirable
to
ask
respondents
to
specify
the
reasons
for
their
reported
choices.

Univariate
descriptive
results
are
meaningful
mainly
when
the
alternative
responses
to
a
question
are
simple
and
can
be
well
specified
and
there
is
a
high
consensus
among
both
respondents
and
investigators
about
the
precise
meaning
of
the
questions
and
answers.
In
some
cases
where
consensus
would
initially
not
be
adequate,
simple
definitions
can
be
added
to
a
questionnaire
to
attain
satisfactory
agreement
­­
e.
g.,
in
asking
people
how
many
rooms
they
have
in
their
homes,
one
states
whether
bathrooms,
basements,
etc.
are
to
be
included
in
the
19
count;
most
respondents
will
conform
to
this
specification.

With
questions
about
subjective
phenomena,
such
as
attitudes
and
values,
treating
answers
as
simply
descriptive
is
seldom
meaningful.
Too
much
depends
on
how
questions
are
worded,
and
there
is
neither
sufficient
social
consensus
about
precise
meaning,
nor
an
external
reference
to
facilitate
such
consensus.

There
are
many
examples
in
the
survey
literature
of
how
changes
in
wording
or
context
will
affect
results
based
on
questions
about
subjective
phenomena
(
see
Schuman
and
Presser
(
1981)).
For
example,
in
national
surveys
close
to
a
quarter
of
the
population
will
choose
the
"
don't
know"
response
to
most
attitude
questions
if
it
is
explicitly
offered;
yet
these
same
people
will
select
a
substantive
alternative
if
"
don't
know"
is
not
specifically
provided,
even
though
accepted
when
asserted
spontaneously.
More
puzzlingly,
a
question
about
"
forbidding"
a
particular
action
tends
to
elicit
less
agreement
than
a
question
about
"
not
allowing"
the
same
action,
although
the
two
questions
are
logically
equivalent.
Beyond
these
examples,
most
attitude
objects
are
simply
too
complex
to
be
summarized
by
a
single
survey
question,
e.
g.,
attitudes
toward
abortion
are
too
dependent
on
the
reasons
for
abortion
and
the
time
in
pregnancy
to
be
adequately
captured
by
a
single
question;
attitudes
toward
"
gun
control"
vary
enormously
depending
on
the
exact
framing
of
the
issue
(
e.
g.,
handguns
vs.
all
guns,
registration
vs.
banning,

and
other
concrete
policy
distinctions).

Contingent
valuation
studies
seek
descriptive
information,
20
yet
call
for
a
response
similar
to
those
elicited
by
questions
about
subjective
phenomena.
Thus
they
risk
many
of
the
same
response
effects
and
other
wording
difficulties
that
turn
up
regularly
in
attitude
surveys.
Minimizing
these
effects
presents
a
considerable
challenge
to
anyone
wishing
to
elicit
reliable
CV
estimates.
The
simplest
way
to
approach
the
problem
is
to
consider
a
CV
survey
as
essentially
a
self­
contained
referendum
in
which
respondents
vote
on
whether
to
tax
themselves
or
not
for
a
particular
purpose.
Since
real
referenda
are
exposed
to
most
of
the
response
effects
that
occur
with
attitude
surveys,
and
since
we
take
the
result
of
referenda
as
telling
us
something
about
"
true"
preferences,
it
is
not
necessary
to
claim
they
can
be
eliminated
completely
in
a
CV
study.

The
Panel
is
of
the
opinion
that
open­
ended
CV
questions
­­

e.
g.,
"
What
is
the
smallest
sum
that
would
compensate
you
for
environmental
damage
X?"
or,
"
What
is
the
largest
amount
you
would
be
willing
to
pay
to
avoid
(
or
repair)
environmental
damage
X?"
­­
are
unlikely
to
provide
the
most
reliable
valuations.

There
are
at
least
two
reasons
for
this
conclusion.
In
the
first
place,
the
scenario
lacks
realism
since
respondents
are
rarely
asked
or
required
in
the
course
of
their
everyday
lives
to
place
a
dollar
value
on
a
particular
public
good.
Their
responses
to
such
questions
are
therefore
likely
to
be
unduly
sensitive
to
trivial
characteristics
of
the
scenario
presented.
In
the
second
place,
an
open­
ended
request
for
willingness
to
pay
or
willingness
to
accept
compensation
invites
strategic
21
overstatement.
The
more
seriously
the
respondent
takes
the
question,
the
more
likely
it
is
that
he
or
she
will
see
that
reporting
a
large
response
is
a
costless
way
to
make
a
point.

Both
experience
and
logic
suggest
that
responses
to
open­
ended
questions
will
be
erratic
and
biased.

However,
the
referendum
format,
especially
when
cast
in
the
willingness
to
pay
mode
­­
"
Would
you
be
willing
to
contribute
(
or
be
taxed)
D
dollars
to
cover
the
cost
of
avoiding
or
repairing
environmental
damage
X?"
­­
has
many
advantages.
It
is
realistic:
referenda
on
the
provision
of
public
goods
are
not
uncommon
in
real
life.
There
is
no
strategic
reason
for
the
respondent
to
do
other
than
answer
truthfully,
although
a
tendency
to
overestimate
often
appears
even
in
connection
with
surveys
concerning
routine
market
goods.
The
fact
that
market
surveys
continue
to
be
used
routinely
suggests
that
this
tendency
is
not
a
insuperable
obstacle.
Of
course,
the
respondent
in
a
CV
survey
understands
that
the
referendum
is
hypothetical;
there
is
no
implication
that
the
tax
will
actually
be
levied
and
the
damage
actually
repaired
or
avoided.
This
suggests
that
considerable
efforts
should
be
made
to
induce
respondents
to
take
the
question
seriously,
and
that
the
CV
instrument
should
contain
other
questions
designed
to
detect
whether
the
respondent
has
done
so.
Although
Carson,
et
al.
(
1992),
included
a
useful
question
to
determine
whether
respondents
believed
the
survey
was
biased
in
any
direction,
they
did
not
sufficiently
test
whether
the
completeness
of,
and
time
period
for,
restoration
stated
in
22
the
survey
were
fully
accepted
by
respondents.
But,
as
far
as
strategic
reasons
go,
a
respondent
who
would
not
be
willing
to
pay
D
dollars
has
no
reason
to
answer
"
Yes,"
and
a
respondent
who
would
be
willing
to
pay
D
dollars
has
no
reason
to
answer
"
No."

There
are,
however,
several
other
reasons
why
one's
response
to
a
hypothetical
referendum
question
might
be
the
opposite
of
one's
actual
vote
on
a
real
ballot.
On
one
hand,
a
respondent
unwilling
to
pay
D
dollars
in
reality
might
feel
pressure
to
give
the
"
right"
or
"
good"
answer
when
responding
to
an
in­
person
or
telephone
interviewer.
This
could
happen
if
the
respondent
believes
that
the
interviewer
would
herself
favor
a
yes
answer.

On
the
other
hand,
a
respondent
actually
willing
to
pay
the
stated
amount
might
answer
in
the
negative
for
several
reasons:

(
i)
belief
that
the
proposed
scenarios
distributed
the
burden
unfairly;
(
ii)
doubt
of
either
the
feasibility
of
the
proposed
action,
so
that
any
contribution
would
be
wasted,
or
the
ability
of
the
relevant
agency
to
carry
out
the
action
efficiently;
or
(
iii)
refusal
to
accept
the
hypothetical
choice
problem,
because
of
either
a
generalized
aversion
to
taxes
or
a
view
that
someone
else
­­
the
"
oil
industry",
for
example
­­
should
pay
for
repair
or
avoidance
as
the
responsible
party.
The
same
considerations
suggest
that
a
CV
instrument
should
include
questions
designed
to
detect
the
presence
of
these
sources
of
bias.
This
is
in
fact
often
done,
but
we
do
not
know
how
successfully.

There
are
two
further
problems
that
could
detract
from
the
reliability
of
CV
responses
without
producing
any
determinate
23
bias:
(
i)
a
feeling
that
one's
vote
will
have
no
significant
effect
on
the
outcome
of
the
hypothetical
referendum,
leading
to
no
reply
or
an
unconsidered
one;
and
(
ii)
poor
information
about
the
damage
being
valued.
Of
course,
either
of
these
could
occur
in
real
referenda.

Here
we
must
decide
on
the
standard
of
knowledgeability
of
the
respondents
that
we
want
to
impose
on
a
CV
study.
It
is
clear
that
it
should
be
at
least
as
high
as
that
which
the
average
voter
brings
to
a
real
referendum
on
the
provision
of
a
specific
public
good,
but
should
it
be
higher?
A
"
conservative"

CV
study,
i.
e.,
one
that
avoids
overestimating
true
willingness
to
pay,
will
no
doubt
exceed
the
minimum
standard
of
information
and
will
also
lean
over
backwards
to
avoid
providing
information
in
a
way
that
might
bias
the
response
upwards.
In
particular,
a
conservative
study
will
provide
the
respondent
with
some
perspective
concerning
the
overall
frequency
and
magnitude
of
oil
spills,
the
amount
of
money
currently
being
spent
on
preventing
and
remedying
them,
the
overall
scale
of
their
consequences,
the
peculiar
features
of
the
spill
in
question,
and
similar
relevant
information.
Placing
the
choice
problem
in
a
broader
context
helps
the
respondent
to
arrive
at
a
realistic
or
even
conservative
valuation.

Most
of
the
provision
of
public
goods
in
this
country
is
decided
by
representatives
and
bureaucrats
rather
that
by
direct
vote
of
the
citizens.
It
is
presumed
that
these
agents
are
more
"
expert"
or
at
least
draw
on
more
knowledge
than
the
citizens
24
themselves.
The
agents'
expertise,
if
it
really
exists,
is
about
the
means
and
cost
of
providing
public
goods,
though
elected
officials
may
sometimes
be
presumed
to
"
represent"
judgments
of
ultimate
value
to
the
citizens.
Nevertheless,
to
increase
one's
confidence
that
a
CV
study
is
conservatively
reliable,
one
might
want
to
compare
its
outcome
with
that
provided
by
a
panel
of
experts.
This
will
help
check
whether
respondents
and
those
conducting
the
study
or
studies
are
reasonably
well­
informed
and
well­
motivated.
This
comparison
could
be
made
on
a
sample
of
CV
studies
to
give
an
idea
of
their
reliability
in
general.

The
above
considerations
suggest
that
a
CV
study
based
on
the
referendum
scenario
can
produce
more
reliably
conservative
estimates
of
willingness
to
pay,
and
hence
of
compensation
required
in
the
aftermath
of
environmental
impairment,
provided
that
a
concerted
effort
is
made
to
motivate
the
respondents
to
take
the
study
seriously,
to
inform
them
about
the
context
and
special
circumstances
of
the
spill
or
other
accident,
and
to
minimize
any
bias
toward
high
or
low
answers
originating
from
social
pressure
within
the
interview.
This
implies
that,
in
the
present
state
of
the
art,
a
reliably
conservative
CV
study
should
be
conducted
with
personal
interviews
of
significant
duration
and
will
therefore
be
relatively
costly.
If
follows
therefore
that,

in
order
that
the
cost
of
the
study
not
be
disproportionately
large
compared
to
the
amount
of
damages,
the
CV
approach
would
likely
be
used
only
in
relatively
major
spills,
at
least
until
further
improvements
in
methodology
can
be
developed
and
25
accepted.
(
A
suggestion
for
doing
so
is
offered
in
Section
V.)

The
referendum
format
offers
one
further
advantage
for
CV.

As
we
have
argued,
external
validation
of
elicited
lost
passiveuse
values
is
usually
impossible.
There
are
however
real­
life
referenda.
Some
of
them,
at
least,
are
decisions
to
purchase
specific
public
goods
with
defined
payment
mechanisms,
e.
g.,
an
increase
in
property
taxes.
The
analogy
with
willingness
to
pay
for
avoidance
or
repair
of
environmental
damage
is
far
from
perfect
but
close
enough
that
the
ability
of
CV­
like
studies
to
predict
the
outcomes
of
real­
world
referenda
would
be
useful
evidence
on
the
validity
of
the
CV
method
in
general.

The
test
we
envision
is
not
an
election
poll
of
the
usual
type.
Instead,
using
the
referendum
format
and
providing
the
usual
information
to
the
respondents,
a
study
should
ask
whether
they
are
willing
to
pay
the
average
amount
implied
by
the
actual
referendum.
The
outcome
of
the
CV­
like
study
should
be
compared
with
that
of
the
actual
referendum.
The
Panel
thinks
that
studies
of
this
kind
should
be
pursued
as
a
method
of
validating
and
perhaps
even
calibrating
applications
of
the
CV
method
(
see
Magleby,
1984).

Addressing
the
Embedding
Problem
Perhaps
the
most
important
internal
argument
against
the
reliability
of
the
CV
approach
(
as
against
general
criticisms
about
vagueness,
lack
of
information,
or
unreality
of
the
scenario)
is
the
observation
of
the
"
embedding"
phenomenon
(
see
26
the
discussion
in
Section
II).
Different
but
similar
samples
of
respondents
are
asked
about
their
willingness
to
pay
for
prevention
of
environmental
damage
scenarios
that
are
identical
except
for
their
scale:
different
numbers
of
seabirds
saved,

different
numbers
of
forest
tracts
preserved
from
logging,
etc.

It
is
reported
that
average
willingness
to
pay
is
often
substantial
for
the
smallest
scenario
presented
but
is
then
substantially
independent
of
the
size
of
the
damage
averted,

rising
slightly
if
at
all
for
large
changes
in
size.

The
usual
interpretation
proposed
by
critics
of
the
CV
method
is
that
the
responses
are
not
measuring
the
equivalent
dollar
value
of
the
utility
of
the
environmental
assets
preserved,
because
that
would
certainly
be
measurably
larger
for
substantially
larger
programs
of
preservation.
Instead,
the
fixed
sum
offered
is
the
value
of
a
feeling
of
having
done
something
praiseworthy;
a
"
warm
glow"
is
the
phrase
often
used.

This
is
potentially
a
very
damaging
criticism
of
the
method.

CV
studies
almost
always
seek
to
measure
willingness
to
pay
to
avoid
a
particular
incident
rather
than
compensation
that
would
be
required
for
damage
that
has
already
occurred.
This
is
because
respondents
are
more
likely
to
exaggerate
the
compensation
they
would
require
than
their
willingness
to
pay,

and
because
the
latter
is
expected
to
be
less
than
the
former
and
so
is
conservative.
If
reported
willingness
to
pay
accurately
reflected
actual
willingness
to
pay,
then,
under
the
"
warm
glow"

interpretation,
willingness
to
pay
might
well
exceed
compensation
27
required
because
the
former
contains
an
element
of
selfapprobation
It
might
be
real
but
not
properly
compensable.

Defenders
of
the
CV
approach
reply
to
this
criticism
in
various
ways.
Sometimes
it
is
argued
that
the
evidence
used
to
support
"
embedding"
simply
indicates
diminishing
marginal
utility
of
the
asset
in
question.
In
many
cases,
however,
the
constancy
or
near­
constancy
of
willingness
to
pay
does
not
appear
consistent
with
the
large
reported
amounts
for
the
first
small
increment
of
environmental
preservation.

A
second
defense
of
CV
against
the
embedding
phenomenon
is
that
CV
questions
have
to
be
posed
carefully
and
in
context.
It
is
argued
that
carelessly
formulated
CV
instruments
leave
respondents
with
the
impression
that
they
are
being
asked,
"
Would
you
pay
$
X
to
avert
a
certain
small
environmental
harm?"
In
a
very
large
population
of
birds,
the
death
of
1,000
is
not
seen
as
noticeably
different
from
the
death
of
100,000
­­
and
may
not
actually
be
very
different
­­
so
that
respondents
simply
answer
the
question
just
asked.

This
second
response
leads
to
the
obvious
question:
how
should
a
CV
instrument
be
framed
to
elicit
an
answer
that
responds
to
the
precise
scenario
and
not
to
a
generalized
"
warm
glow"
effect?
We
must
reject
one
possible
approach,
that
of
asking
each
respondent
to
express
willingness
to
pay
to
avert
incidents
of
varying
sizes;
the
danger
is
that
embedding
will
be
forcibly
avoided,
still
without
realism.
This
issue
is
best
considered
as
part
of
the
broader
question:
How
much
context
28
about
the
incident
itself
and
about
the
respondent's
circumstances
and
choices
should
be
included
in
the
CV
instrument?

We
are
recommending
a
high
standard
of
richness
in
context
to
achieve
a
realistic
background.
Our
proposed
guidelines
regarding
this
issue
are
embodied
in
Section
IV
below.

Time
Dimension
of
Passive
Use
Losses
Typically,
environmental
damages
from
oil
spills
or
similar
accidents
are
severe
for
some
period
of
time
­­
weeks,
months,
or
sometimes
a
few
years
­­
and
gradually
are
reduced
by
natural
forces
and
human
efforts
to
a
low
or
possibly
even
zero
steady
state
level.
In
some
circumstances,
passive­
use
losses
derive
only
or
mostly
from
the
steady
state
conditions;
thus,
if
passive
use
value
derives
from
species
diversity,
even
a
considerable
loss
of
birds
or
mammals
which
does
not
endanger
any
species
will
give
rise
to
no
loss.
If,
on
the
contrary,
considerable
passiveuse
value
is
attached
to
the
interim
state
of
the
natural
resource,
then
respondents
have
to
do
a
very
difficult
present
value
calculation
properly
to
compute
their
current
willingness
to
pay
for
the
difference
between
the
fully
restored
state
of
the
resource
and
the
actual
state
as
the
level
of
restoration
varies
over
time.
CV
surveys
accordingly
have
to
be
carefully
designed
to
allow
respondents
to
differentiate
interim
from
steady
state
passive­
use
loss,
and,
if
there
is
interim
passive­
use
loss,
to
report
its
present
value
correctly.
29
It
is
reasonable
to
assume
that
interim
passive­
use
values
are
additive
over
time.
Hence,
we
need
a
calculation
of
present
values
of
the
interim
losses.
The
discounting
and
the
estimation
of
the
rate
of
recovery
of
the
resource
should
be
done
by
technical
experts
and
not
by
the
respondents,
who
are
unlikely
to
handle
these
tasks
adequately.
Respondents
should
be
asked
only
their
willingness
to
pay
to
eliminate
the
difference
between
some
partially
restored
level
of
the
resource
and
the
pristine
state
for
a
specific
period
of
time,
say
a
year,
on
the
assumption
that
after
that
time
full
restoration
is
assured.
Technical
experts
would
estimate
how
the
state
of
the
resource
will
vary
from
year
to
year
as
the
restoration
takes
place.
The
technical
information
about
the
state
of
the
resource,
together
with
the
respondent's
assessments
of
the
flow
valuation
of
the
resource,

can
be
used
to
construct
a
time
series
of
passive­
use
losses
which
can
be
discounted
to
the
present
at
an
appropriate
rate
of
interest
to
determine
the
present
value
of
the
damages.

IV.
SURVEY
GUIDELINES
In
this
section
we
try
to
lay
down
a
fairly
complete
set
of
guidelines
compliance
with
which
would
define
an
ideal
CV
survey.

A
CV
survey
does
not
have
to
meet
each
of
these
guidelines
fully
in
order
to
qualify
as
a
source
of
reliable
information
to
a
damage
assessment
process.
Many
departures
from
the
guidelines
or
even
a
single
serious
deviation
would,
however,
suggest
unreliability
prima
facie.
To
preserve
continuity,
we
give
only
30
a
bald
list
of
guidelines
here.
They
are
repeated
together
with
further
explanatory
comments
in
the
Appendix
to
this
Report.

GENERAL
GUIDELINES
0
Sample
Type
and
Size:
Probability
sampling
is
essential
for
a
survey
used
for
damage
assessment.
1
The
choice
of
sample
specific
design
and
size
is
a
difficult,
technical
question
that
requires
the
guidance
of
a
professional
sampling
statistician.

0
Minimize
Nonresponses:
High
nonresponse
rates
would
make
the
survey
results
unreliable.

0
Personal
Interview:
The
Panel
believes
it
unlikely
that
reliable
estimates
of
values
could
be
elicited
with
mail
surveys.
Face­
to­
face
interviews
are
usually
preferable,

although
telephone
interviews
have
some
advantages
in
terms
of
cost
and
centralized
supervision.

0
Pretesting
for
Interviewer
Effects:
An
important
respect
in
1
This
need
not
preclude
use
of
less
adequate
samples,
including
quota
or
even
convenience
samples,
for
preliminary
testing
of
specific
experimental
variations,
so
long
as
order
of
magnitude
differences
rather
than
univariate
results
are
the
focus.
Even
then,
obvious
sources
of
bias
should
be
avoided
(
e.
g.,
college
students
are
probably
too
different
in
age
and
education
from
the
heterogeneous
adult
population
to
provide
a
trustworthy
basis
for
wider
generalization).
31
which
CV
surveys
differ
from
actual
referenda
is
the
presence
of
an
interviewer
(
except
in
the
case
of
mail
surveys).
It
is
possible
that
interviewers
contribute
to
"
social
desirability"
bias,
since
preserving
the
environment
is
widely
viewed
as
something
positive.
In
order
to
test
this
possibility,
major
CV
studies
should
incorporate
experiments
that
assess
interviewer
effects.

0
Reporting:
Every
report
of
a
CV
study
should
make
clear
the
definition
of
the
population
sampled,
the
sampling
frame
used,
the
sample
size,
the
overall
sample
non­
response
rate
and
its
components
(
e.
g.,
refusals),
and
item
non­
response
on
all
important
questions.
The
report
should
also
reproduce
the
exact
wording
and
sequence
of
the
questionnaire
and
of
other
communications
to
respondents
(
e.
g.,
advance
letters).
All
data
from
the
study
should
be
archived
and
made
available
to
interested
parties
(
see
Carson
et
al.
(
1992),
for
an
example
of
good
practice
in
inclusion
of
questionnaire
and
related
details;
as
of
this
date,
however,
the
report
has
not
been
available
publicly
and
the
data
have
not
been
archived
for
open
use
by
other
scholars).

0
Careful
Pretesting
of
a
CV
Questionnaire:
Respondents
in
a
CV
survey
are
ordinarily
presented
with
a
good
deal
of
new
and
often
technical
information,
well
beyond
what
is
typical
32
in
most
surveys.
This
requires
very
careful
pilot
work
and
pretesting,
plus
evidence
from
the
final
survey
that
respondents
understood
and
accepted
the
main
description
and
questioning
reasonably
well.

GUIDELINES
FOR
VALUE
ELICITATION
SURVEYS
The
following
guidelines
are
met
by
the
best
CV
surveys
and
need
to
be
present
in
order
to
assure
reliability
and
usefulness
of
the
information
that
is
obtained.

0
Conservative
Design:
Generally,
when
aspects
of
the
survey
design
and
the
analysis
of
the
responses
are
ambiguous,
the
option
that
tends
to
underestimate
willingness
to
pay
is
preferred.
A
conservative
design
increases
the
reliability
of
the
estimate
by
eliminating
extreme
responses
that
can
enlarge
estimated
values
wildly
and
implausibly.

0
Elicitation
Format:
The
willingness
to
pay
format
should
be
used
instead
of
the
compensation
required
because
the
former
is
the
conservative
choice.

0
Referendum
Format:
The
valuation
question
should
be
posed
as
a
vote
on
a
referendum.

0
Accurate
Description
of
the
Program
or
Policy:
Adequate
33
information
must
be
provided
to
respondents
about
the
environmental
program
that
is
offered.
It
must
be
defined
in
a
way
that
is
relevant
to
damage
assessment.

0
Pretesting
of
Photographs:
The
effects
of
photographs
on
subjects
must
be
carefully
explored.

0
Reminder
of
Undamaged
Substitute
Commodities:
Respondents
must
be
reminded
of
substitute
commodities,
such
as
other
comparable
natural
resources
or
the
future
state
of
the
same
natural
resource.
This
reminder
should
be
introduced
forcefully
and
directly
prior
to
the
main
valuation
question
to
assure
that
respondents
have
the
alternatives
clearly
in
mind.

0
Adequate
Time
Lapse
from
the
Accident:
The
survey
must
be
conducted
at
a
time
sufficiently
distant
from
the
date
of
the
environmental
insult
that
respondents
regard
the
scenario
of
complete
restoration
as
plausible.
Questions
should
be
included
to
determine
the
state
of
subjects'

beliefs
regarding
restoration
probabilities.

0
Temporal
Averaging:
Time
dependent
measurement
noise
should
be
reduced
by
averaging
across
independently
drawn
samples
taken
at
different
points
in
time.
A
clear
and
substantial
34
time
trend
in
the
responses
would
cast
doubt
on
the
"
reliability"
of
the
finding.

0
"
No­
answer"
Option:
A
"
no­
answer"
option
should
be
explicitly
allowed
in
addition
to
the
"
yes"
and
"
no"
vote
options
on
the
main
valuation
(
referendum)
question.

Respondents
who
choose
the
"
no­
answer"
option
should
be
asked
nondirectively
to
explain
their
choice.
Answers
should
be
carefully
coded
to
show
the
types
of
responses,

for
example:
(
i)
rough
indifference
between
a
yes
and
a
no
vote;
(
ii)
inability
to
make
a
decision
without
more
time
or
more
information;
(
iii)
preference
for
some
other
mechanism
for
making
this
decision;
and
(
iv)
bored
by
this
survey
and
anxious
to
end
it
as
quickly
as
possible.

0
Yes/
no
Follow­
ups:
Yes
and
no
responses
should
be
followed
up
by
the
open­
ended
question:
"
Why
did
you
vote
yes/
no?"

Answers
should
be
carefully
coded
to
show
the
types
of
responses,
for
example:
(
i)
It
is
(
or
isn't)
worth
it;

(
ii)
Don't
know;
or
(
iii)
The
oil
companies
should
pay.

0
Cross­
tabulations:
The
survey
should
include
a
variety
of
other
questions
that
help
to
interpret
the
responses
to
the
primary
valuation
question.
The
final
report
should
include
summaries
of
willingness
to
pay
broken
down
by
these
categories.
Among
the
items
that
would
be
helpful
in
35
interpreting
the
responses
are:

Income
Prior
Knowledge
of
the
Site
Prior
Interest
in
the
Site
(
Visitation
Rates)

Attitudes
Toward
the
Environment
Attitudes
Toward
Big
Business
Distance
to
the
Site
Understanding
of
the
Task
Belief
in
the
Scenarios
Ability/
Willingness
to
Perform
the
Task
0
Checks
on
Understanding
and
Acceptance:
The
above
guidelines
must
be
satisfied
without
making
the
instrument
so
complex
that
it
poses
tasks
that
are
beyond
the
ability
or
interest
level
of
many
participants.

GOALS
FOR
VALUE
ELICITATION
SURVEYS
The
following
items
are
not
adequately
addressed
by
even
the
best
CV
surveys.
In
the
opinion
of
the
Panel,
these
issues
will
need
to
be
convincingly
dealt
with
in
order
to
assure
the
reliability
of
the
estimates.

0
Alternative
Expenditure
Possibilities:
Respondents
must
be
reminded
that
their
willingness
to
pay
for
the
environmental
program
in
question
would
reduce
their
expenditures
for
private
goods
or
other
public
goods.
This
reminder
should
36
be
more
than
perfunctory,
but
less
than
overwhelming.
The
goal
is
to
induce
respondents
to
keep
in
mind
other
likely
expenditures,
including
those
on
other
environmental
goods,

when
evaluating
the
main
scenario.

0
Deflection
of
Transaction
Value:
The
survey
should
be
designed
to
deflect
the
general
"
warm­
glow"
of
giving
or
the
dislike
of
"
big
business"
away
from
the
specific
environmental
program
that
is
being
evaluated.
It
is
possible
that
the
referendum
format
limits
the
"
warm
glow"

effect,
but
until
this
is
clear
the
survey
design
should
explicitly
address
this
problem.

0
Steady
State
or
Interim
Losses:
It
should
be
made
apparent
that
respondents
can
distinguish
interim
from
steady­
state
losses.

0
Present
Value
Calculations
of
Interim
Losses:
It
should
be
demonstrated
that,
in
revealing
values,
respondents
are
adequately
sensitive
to
the
timing
of
the
restoration
process.

0
Advance
Approval:
Since
the
design
of
the
CV
survey
can
have
a
substantial
effect
on
the
responses,
it
is
desirable
that
­­
if
possible
­­
critical
features
be
preapproved
by
37
both
sides
in
a
legal
action,
with
arbitration
and/
or
experiments
used
when
disagreements
cannot
be
resolved
by
the
parties
themselves.

0
Burden
of
Proof:
Until
such
time
as
there
is
a
set
of
reliable
reference
surveys,
the
burden
of
proof
of
reliability
must
rest
on
the
survey
designers.
They
must
show
through
pretesting
or
other
experiments
that
their
survey
does
not
suffer
from
the
problems
that
these
guidelines
are
intended
to
avoid.
Specifically,
if
a
CV
survey
suffered
from
any
of
the
following
maladies,
we
would
judge
its
findings
"
unreliable":

­­
A
high
nonresponse
rate
to
the
entire
survey
instrument
or
to
the
valuation
question.

­­
Inadequate
responsiveness
to
the
scope
of
the
environmental
insult.

­­
Lack
of
understanding
of
the
task
by
the
respondents.

­­
Lack
of
belief
in
the
full
restoration
scenario.

­­
"
Yes"
or
"
no"
votes
on
the
hypothetical
referendum
that
are
not
followed
up
or
explained
by
making
38
reference
to
the
cost
and/
or
the
value
of
the
program.

0
Reliable
Reference
Surveys:
In
order
to
alleviate
this
heavy
burden
of
proof,
we
strongly
urge
the
government
to
undertake
the
task
of
creating
a
set
of
reliable
reference
surveys
that
can
be
used
to
interpret
the
guidelines
and
also
to
calibrate
surveys
that
do
not
fully
meet
the
conditions.

V.
RECOMMENDATIONS
FOR
FUTURE
RESEARCH
The
Panel's
major
research
recommendation
goes
toward
a
drastic
reform
of
the
CV
procedure,
extending
beyond
the
guidelines
suggestion
in
Section
IV.

The
problem
of
estimating
the
demand
for
highly
innovative
commercial
products,
including
some
that
have
not
yet
actually
been
produced,
is
much
like
the
problem
faced
in
CV
research.
It
is
the
problem
of
estimating
willingness
to
pay
for
a
necessarily
unfamiliar
product.
The
field
of
market
research
has
developed
methods
­­
"
conjoint
analysis,"
for
example
­­
that
are
very
similar
to
the
CV
approach.
(
One
important
difference
is
that
a
new
product
may
eventually
reach
the
market,
and
projections
of
expected
sales
can
be
checked.
Survey
responses
are
usually
found
to
be
moderate
overestimates
of
actual
willingness
to
pay.)

Practitioners
have
found
that
survey
methods
are
better
at
estimating
relative
demand
than
absolute
demand.
There
is
an
39
anchoring
problem,
even
with
private
goods
­­
that
is,
absolute
willingness
to
pay
is
hard
to
pin
down.
This
leads
to
the
following
suggestion.

The
federal
government
should
produce
standard
damage
assessments
for
a
few
specific
reference
oil
spills,
either
hypothetical
or
actual,
ranging
from
small
to
large.
These
standard
valuations
could
be
generated
by
any
method.
One
possibility
would
be
through
a
jury
of
experts.
Such
a
jury
of
experts
might
wish
to
conduct
a
series
of
CV
studies,
satisfying
the
guidelines
laid
out
above.
These
CV
studies
would
be
inputs
into
the
jury
process,
to
be
combined
with
other
information
and
expert
judgment.
Once
these
benchmarks
were
available,
they
could
serve
as
reference
points
for
later
CV
studies.
When
a
damage
assessment
is
required,
surveys
could
be
used
to
elicit
answers
to
questions
like:
"
Would
you
pay
(
much
more,
more,

about
the
same,
less,
much
less)
to
prevent
this
spill
than
you
would
to
prevent
Standard
Spill
A?"
"
Would
you
pay
an
amount
to
avoid
this
spill
that
is
between
the
amounts
you
would
pay
to
avoid
Standard
Spill
B
and
Standard
Spill
C?
If
so,
is
the
amount
much
closer
to
B
than
C,
closer
to
B
than
C,
halfway
between
B
and
C,
closer
to
C
than
B,
much
closer
to
C
than
B?"

These
questions
presumably
would
not
be
asked
so
schematically.

Responses
to
such
a
study
could
then
serve
as
one
reliable
source
of
information
in
the
damage
assessment.

We
recognize
that
this
technique
would
require
that
respondents
be
made
familiar
with
the
reference
spills
as
well
as
40
the
particular
spill
whose
damage
is
being
assessed.
We
expect
that
the
additional
effort
would
be
more
than
offset
by
the
greater
simplicity
and
reliability
in
estimating
relative
willingness
to
pay.

This
possibility
suggests
a
slightly
more
radical
extension
of
the
CV
method.
Respondents
could
be
asked
to
compare
their
willingness
to
pay
to
avoid
a
specific
case
of
environmental
damage
to
their
willingness
to
pay
for
a
range
of
fairly
familiar
private
goods.
It
would
no
doubt
be
best
if
the
private
goods
were
to
bear
some
similarity
to
the
environmental
good
in
question,
but
that
is
not
necessary.
The
anchoring
purpose
would
be
served
if
respondents
could
measure
their
willingness
to
pay
in
units
of
articles
of
clothing
or
small
household
appliances
forgone.

This
latter
is
a
suggestion
for
research
in
the
CV
method,

not
necessarily
a
recommendation
for
current
practical
use.

The
guidelines
proposed
in
Section
IV
themselves
suggest
areas
for
further
research,
this
time
within
the
contingent
valuation
community.
In
particular,
we
emphasize
the
urgency
of
studying
the
sensitivity
of
willingness
to
pay
responses
to
the
number
and
extent
of
budgetary
substitutes
mentioned
in
survey
instruments
(
that
is,
reminders
of
other
things
on
which
respondents
could
spend
their
money).
In
such
research
it
would
be
helpful
if
parallel
studies
were
conducted
on
the
sensitivity
of
stated
intentions
to
buy
ordinary
market
goods
­­
both
familiar
and
unfamiliar
­­
to
reminders
of
alternative
uses
of
41
those
resources.
The
point
is
to
discover
the
extent
to
which
the
valuation
of
environmental
public
goods
is
intrinsically
more
difficult
than
similar
exercises
with
respect
to
market
goods.

A
closely­
related
line
of
research
is
the
sensitivity
of
responses
in
CV
surveys
to
the
number
and
extent
of
undamaged
substitute
commodities
mentioned
explicitly
in
the
survey
instrument
(
miles
of
nearby
shoreline,
miles
of
shoreline
elsewhere,
similarity
for
animal
or
bird
life,
alternative
recreation
possibilities
and
so
on).
This
could
be
extended
to
variations
in
the
way
in
which
the
budget
constraint
is
presented
to
respondents.
Here
again,
comparisons
with
market
goods
would
be
useful.

Finally,
having
urged
that
the
availability
of
a
no­
vote
option
is
an
important
component
of
the
ability
of
the
CV
technique
to
mimic
an
actual
referendum,
we
recommend
further
research
into
alternative
ways
of
presenting
and
interpreting
the
no­
vote
option.
In
this
respect,
too,
comparative
studies
with
familiar
public
and
private
goods
(
local
parks,
school
facilities,
housing
for
the
homeless,
food
distributions)
would
be
enlightening.
Real
referenda
always
allow
the
option
of
not
voting,
in
a
natural
way.
CV
studies
have
to
achieve
the
same
result
more
deliberately,
so
there
is
a
need
to
know
if
the
precise
formulation
matters
very
much
to
the
result.

VI.
CONCLUSIONS
AND
RECOMMENDATIONS
The
Panel
starts
from
the
premise
that
passive­
use
loss
­­
42
interim
or
permanent
­­
is
a
meaningful
component
of
the
total
damage
resulting
from
environmental
accidents.
A
problem
arises
because
passive­
use
losses
have
few
or
no
overt
behavioral
consequences.
The
faintness
of
the
behavioral
trail
means
that
a
well­
designed
and
adequately
sensitive
measuring
instrument
is
needed
to
substitute
for
conventional
observations
of
behavior.

In
particular,
can
the
CV
method
provide
a
sufficiently
reliable
estimate
of
total
loss
­­
including
passive­
use
loss
­­
to
play
a
useful
role
in
damage
assessment?

It
has
been
argued
in
the
literature
and
in
comments
addressed
to
the
Panel
that
the
results
of
CV
studies
are
variable,
sensitive
to
details
of
the
survey
instrument
used,
and
vulnerable
to
upward
bias.
These
arguments
are
plausible.

However,
some
antagonists
of
the
CV
approach
go
so
far
as
to
suggest
that
there
can
be
no
useful
information
content
to
CV
results.
The
Panel
is
unpersuaded
by
these
extreme
arguments.

In
Section
IV
above,
we
identify
a
number
of
stringent
guidelines
for
the
conduct
of
CV
studies.
These
require
that
respondents
be
carefully
informed
about
the
particular
environmental
damage
to
be
valued,
and
about
the
full
extent
of
substitutes
and
undamaged
alternatives
available.
In
willingness
to
pay
scenarios,
the
payment
vehicle
must
be
presented
fully
and
clearly,
with
the
relevant
budget
constraint
emphasized.
The
payment
scenario
should
be
convincingly
described,
preferably
in
a
referendum
context,
because
most
respondents
will
have
had
experience
with
referendum
ballots
with
less­
than­
perfect
43
background
information.
Where
choices
in
formulating
the
CV
instrument
can
be
made,
we
urge
they
lean
in
the
conservative
direction,
as
a
partial
or
total
offset
to
the
likely
tendency
to
exaggerate
willingness
to
pay.

The
Panel
concludes
that
under
those
conditions
(
and
others
specified
above),
CV
studies
convey
useful
information.
We
think
it
is
fair
to
describe
such
information
as
reliable
by
the
standards
that
seem
to
be
implicit
in
similar
contexts,
like
market
analysis
for
new
and
innovative
products
and
the
assessment
of
other
damages
normally
allowed
in
court
proceedings.
As
in
all
such
cases,
the
more
closely
the
guidelines
are
followed,
the
more
reliable
the
result
will
be.

It
is
not
necessary,
however,
that
every
single
injunction
be
completely
obeyed;
inferences
accepted
in
other
contexts
are
not
perfect
either.

Thus,
the
Panel
concludes
that
CV
studies
can
produce
estimates
reliable
enough
to
be
the
starting
point
of
a
judicial
process
of
damage
assessment,
including
lost
passive­
use
values.

To
be
acceptable
for
this
purpose,
such
studies
should
follow
the
guidelines
described
in
Section
IV
above.
The
phrase
"
be
the
starting
point"
is
meant
to
emphasize
that
the
Panel
does
not
suggest
that
CV
estimates
can
be
taken
as
automatically
defining
the
range
of
compensable
damages
within
narrow
limits.
Rather,

we
have
in
mind
the
following
considerations.

The
Panel
is
persuaded
that
hypothetical
markets
tend
to
overstate
willingness
to
pay
for
private
as
well
as
public
goods.
44
The
same
bias
must
be
expected
to
occur
in
CV
studies.
To
the
extent
that
the
design
of
CV
instruments
makes
conservative
choices
when
alternatives
are
available,
as
urged
in
Section
IV,

this
intrinsic
bias
may
be
offset
or
even
over­
corrected.
All
surveys
of
attitudes
or
intentions
are
bound
to
exhibit
sensitivity
of
response
to
the
framing
of
questions
and
the
order
in
which
they
are
asked.
No
automatic
or
mechanical
calibration
of
responses
seems
to
be
possible.

The
judicial
process
must
in
each
case
come
to
a
conclusion
about
the
degree
to
which
respondents
have
been
induced
to
consider
alternative
uses
of
funds
and
take
the
proposed
payment
vehicle
seriously.
Defendants
will
argue
that
closer
attention
to
substitute
commodities
would
have
yielded
lower
valuations.

Trustees
will
argue
that
they
have
already
leaned
over
backwards
to
ensure
conservative
responses.
Judges
and
juries
must
decide
as
they
do
in
other
damage
cases.
The
Panel's
conclusion
is
that
a
well­
conducted
CV
study
provides
an
adequately
reliable
benchmark
to
begin
such
arguments.
It
contains
information
that
judges
and
juries
will
wish
to
use,
in
combination
with
other
evidence,
including
the
testimony
of
expert
witnesses.

The
Panel's
second
conclusion
is
that
the
appropriate
federal
agencies
should
begin
to
accumulate
standard
damage
assessments
for
a
range
of
oil
spills,
as
described
in
Section
V.

That
process
should
further
improve
the
reliability
of
CV
studies
in
damage
assessment.
It
should
thus
contribute
to
increasing
the
accuracy
and
reducing
the
cost
of
subsequent
45
damage
assessment
cases.
In
that
sense,
it
can
be
regarded
as
an
investment.

The
proposals
for
further
research
outlined
in
Section
V
are
an
integral
part
of
our
recommendations.
The
Panel
believes
that
the
suggestions
put
forward
there
could
lead
to
more
reliable
and
less
controversial
damage
assessment
at
reduced
cost.
It
is
not
to
be
expected
that
controversy
will
disappear,
however.
There
will
always
be
controversy
where
intangible
losses
have
to
be
evaluated
in
monetary
terms.
46
APPENDIX
GENERAL
GUIDELINES
0
Sample
Type
and
Size:
Probability
sampling
is
essential
for
a
survey
used
for
damage
assessment.
2
The
choice
of
sample
specific
design
and
size
is
a
difficult,
technical
question
that
requires
the
guidance
of
a
professional
sampling
statistician.

If
a
single
dichotomous
question
of
the
yes­
no
type
is
used
to
elicit
valuation
responses,
then
a
total
sample
size
of
1000
respondents
will
limit
sampling
error
to
about
3%
plus
or
minus
on
a
single
dichotomous
question,
assuming
simple
random
sampling.
However,
this
or
any
other
sample
size
needs
to
be
reconceptualized
for
three
reasons.
First,
if
face­
to­
face
interviewing
is
used,
as
we
suggest
above,
clustering
and
stratification
must
be
taken
into
account.
Second,
if
dichotomous
valuation
questions
are
used
(
e.
g.,
hypothetical
referenda),
separate
valuation
amounts
must
be
asked
of
random
sub­
samples
and
these
responses
must
be
unscrambled
econometrically
to
estimate
the
underlying
population
mean
or
median.
Third,
in
order
to
incorporate
experiments
on
2
This
need
not
preclude
use
of
less
adequate
samples,
including
quota
or
even
convenience
samples,
for
preliminary
testing
of
specific
experimental
variations,
so
long
as
order
of
magnitude
differences
rather
than
univariate
results
are
the
focus.
Even
then,
obvious
sources
of
bias
should
be
avoided
(
e.
g.,
college
students
are
probably
too
different
in
age
and
education
from
the
heterogeneous
adult
population
to
provide
a
trustworthy
basis
for
wider
generalization).
47
interviewer
and
wording
effects,
additional
random
sub­
sampling
is
required.
For
all
these
reasons,
it
will
be
important
to
consult
sampling
statisticians
in
the
design
of
a
CV
survey
intended
for
legal
or
policy­
making
purposes.

0
Minimize
Nonresponses:
High
nonresponse
rates
would
make
the
survey
results
unreliable.

To
the
extent
that
a
CV
study
is
expected
to
represent
the
adult
population
of
the
United
States
or
a
portion
of
it,

minimizing
both
sample
non­
response
and
item
non­
response
are
important.
The
former
is
unlikely
to
be
below
20%
even
in
very
high
quality
surveys;
the
latter
has
also
been
large
in
some
CV
surveys
because
of
the
difficulty
of
the
task
respondents
are
being
asked
to
perform.
These
sources
of
potential
bias
can
be
partially
justified
on
the
grounds
that
they
also
occur
with
official
referenda,
in
both
cases
with
the
loss
especially
of
the
least
educated
parts
of
the
population.
The
further
reduction
of
the
final
sample
by
elimination
of
"
protest
zeros,"
"
unrealistic
high
values,"
and
other
problematic
responses
may
lead
to
effective
final
total
response
rates
so
low
as
to
imply
that
the
survey
population
consists
of
interested
and
specially
instructed
quasi­
experts.
This
consideration
reinforces
the
desirability
of
combining
a
reasonable
response
rate
with
a
high
but
not
forbidding
standard
of
information,
as
discussed
in
Section
III
above.
48
0
Personal
Interview:
The
Panel
believes
it
unlikely
that
reliable
estimates
of
values
could
be
elicited
with
mail
surveys.
Face­
to­
face
interviews
are
usually
preferable,

although
telephone
interviews
have
some
advantages
in
terms
of
cost
and
centralized
supervision.

Assuming
a
CV
survey
is
to
represent
a
natural
population,

such
as
all
adults
in
the
United
States,
or
those
in
a
single
urban
area
or
a
state,
it
is
desirable
that
it
be
carried
out
using
either
face­
to­
face
or
telephone
interviews.
Mail
surveys
typically
employ
lists
that
cover
too
small
a
part
of
the
population
(
e.
g.,
samples
based
on
telephone
directories
omit
approximately
half
the
U.
S.
population
because
of
non­
listed
numbers,
incorrect
numbers,
and
non­
phone
households),
and
then
miss
another
quarter
or
more
of
the
remainder
through
nonresponse
In
addition,
since
the
content
of
a
mail
questionnaire
can
be
reviewed
by
targeted
respondents
before
deciding
to
return
it,
those
most
interested
in
a
natural
resource
issue
or
in
one
side
or
the
other
can
make
their
decision
on
that
basis.
It
is
also
impossible
using
mail
surveys
to
guarantee
random
selection
within
households
or
to
confine
answering
to
a
single
respondent,

and
it
is
difficult
(
though
not
impossible)
to
control
questionorder
effects.
Thus,
mail
surveys
should
be
used
only
if
another
supplementary
method
can
be
employed
to
cross­
validate
the
results
on
a
random
sub­
sample
of
respondents.
49
The
choice
between
telephone
and
face­
to­
face
administration
is
less
clear.
Face­
to­
face
surveys
offer
practical
advantages
in
maintaining
respondent
motivation
and
allowing
use
of
graphic
supplements.
Both
coverage
and
response
rates
are
also
usually
somewhat
higher
than
with
telephone
surveys.
However,
telephone
surveys
can
cut
interviewing
costs
by
between
a
third
and
a
half;

for
CV
purposes,
it
may
be
a
disadvantage
that
most
survey
investigators
believe
telephone
interviews
need
to
be
kept
shorter
in
length
than
face­
to­
face
interviews
because
respondent
attention
and
cooperation
are
more
difficult
to
maintain.
In
addition,
random­
digit­
dial
telephone
surveys
approximate
simple
random
sampling.
Face­
to­
face
surveys
must
be
based
on
cluster
sampling
and,
therefore,
the
results
provide
less
precise
estimates
than
do
telephone
surveys
of
the
same
size.

0
Pretesting
for
Interviewer
Effects:
An
important
respect
in
which
CV
surveys
differ
from
actual
referenda
is
the
presence
of
an
interviewer
(
except
in
the
case
of
mail
surveys).
It
is
possible
that
interviewers
contribute
to
"
social
desirability"
bias,
since
preserving
the
environment
is
widely
viewed
as
something
positive.
In
order
to
test
this
possibility,
major
CV
studies
should
incorporate
experiments
that
assess
interviewer
effects.

To
test
for
interviewer
effects,
two
modifications
might
be
made
to
a
standard
face­
to­
face
CV
survey.
In
one
variant
on
50
current
practice,
respondents
would
stop
when
they
come
to
the
valuation
question,
write
their
"
vote"
on
a
ballot,
and
fold
and
deposit
it
in
a
sealed
box.
However,
since
this
practice
would
not
mimic
the
complete
anonymity
of
the
voting
booth,
for
a
subsample
of
respondents
a
second
modification
should
be
made.

Respondents
would
be
allowed
to
mail
their
"
ballots"
in
unmarked
envelopes
directly
to
the
survey
organization,
even
though
that
will
preclude
any
but
the
simplest
analysis
of
responses.
Tests
of
the
effect
of
both
these
modifications
of
current
practice
will
indicate
whether
they
are
needed
routinely
or
whether
at
least
some
calibration
should
be
introduced
to
compensate
for
interviewer
effects.
(
The
more
modest
of
these
proposed
modifications
­­
a
simulated
ballot
box,
or
even
voting
on
a
portable
computer
­­
has
few
if
any
disadvantages
and
might
be
made
standard
if
it
shows
any
reliable
departure
at
all
from
answers
given
orally
to
the
interviewer.)

0
Reporting:
Every
report
of
a
CV
study
should
make
clear
the
definition
of
the
population
sampled,
the
sampling
frame
used,
the
sample
size,
the
overall
sample
non­
response
rate
and
its
components
(
e.
g.,
refusals),
and
item
non­
response
on
all
important
questions.
The
report
should
also
reproduce
the
exact
wording
and
sequence
of
the
questionnaire
and
of
other
communications
to
respondents
(
e.
g.,
advance
letters).
All
data
from
the
study
should
be
archived
and
made
available
to
interested
parties
(
see
51
Carson
et
al.
(
1992),
for
an
example
of
good
practice
in
inclusion
of
questionnaire
and
related
details;
as
of
this
date,
however,
the
report
has
not
been
available
publicly
and
the
data
have
not
been
archived
for
open
use
by
other
scholars).

0
Careful
Pretesting
of
a
CV
Questionnaire:
Respondents
in
a
CV
survey
are
ordinarily
presented
with
a
good
deal
of
new
and
often
technical
information,
well
beyond
what
is
typical
in
most
surveys.
This
requires
very
careful
pilot
work
and
pretesting,
plus
evidence
from
the
final
survey
that
respondents
understood
and
accepted
the
main
description
and
questioning
reasonably
well.

Parenthetically,
the
claim
sometimes
made
by
CV
proponents
that
particular
methods
of
piloting,
such
as
focus
groups,
are
essential
should
be
viewed
with
skepticism,
since
these
claims
are
unsupported
by
any
systematic
evidence.
Nor
is
it
clear
that
what
are
called
"
state­
of­
the­
art"
CV
surveys
constitute
something
entirely
new
or
different
from
other
types
of
serious
survey
investigations.
Thus,
although
evidence
that
questionnaire
development
has
been
carried
out
carefully
is
certainly
important,
it
cannot
be
taken
as
a
self­
sufficient
basis
of
validity
­­
the
more
so
because
we
know
that
many
people
will
answer
survey
questions
without
apparent
difficulty,
even
when
they
do
not
understand
them
well.
A
way
of
reducing
52
pressure
to
give
answers
of
questionable
meaningfulness
would
be
to
provide
respondents
an
explicit
"
no
opinion"
type
of
alternative
when
a
key
valuation
question
is
posed.

GUIDELINES
FOR
VALUE
ELICITATION
SURVEYS
The
following
guidelines
are
met
by
the
best
CV
surveys
and
need
to
be
present
in
order
to
assure
reliability
and
usefulness
of
the
information
that
is
obtained.

0
Conservative
Design:
Generally,
when
aspects
of
the
survey
design
and
the
analysis
of
the
responses
are
ambiguous,
the
option
that
tends
to
underestimate
willingness
to
pay
is
preferred.
A
conservative
design
increases
the
reliability
of
the
estimate
by
eliminating
extreme
responses
that
can
enlarge
estimated
values
wildly
and
implausibly.

0
Elicitation
Format:
The
willingness
to
pay
format
should
be
used
instead
of
compensation
required
because
the
former
is
the
conservative
choice.

In
experimental
settings,
the
gap
between
stated
intentions
to
support
a
particular
referendum
and
actual
behavior
in
the
voting
booth
can
be
very
great
(
see
Magleby,
1984).
This
gap
might
be
treated
by
"
calibration"
if
there
were
historical
data
on
the
relationship
between
such
intentions
and
behavior.

Unfortunately,
we
are
aware
of
no
data
that
is
close
enough
to
53
the
CV
context
that
could
be
used
to
calibrate
CV
responses.
In
the
absence
of
historical
data
that
can
be
used
to
calibrate
the
intentions
reported
in
the
CV
surveys,
the
survey
instrument
has
to
be
designed
with
extraordinary
care
so
that
it
can
stand
on
its
own.

0
Referendum
Format:
The
valuation
question
should
be
posed
as
a
vote
on
a
referendum.

As
is
now
generally
recognized
by
most
CV
proponents,
asking
respondents
to
give
a
dollar
valuation
in
response
to
an
openended
question
presents
them
with
an
extremely
difficult
task.

At
the
same
time,
CV
proponents
also
recognize
that
presenting
respondents
a
set
of
dollar
amounts
from
which
they
are
to
choose
is
likely
to
create
anchoring
and
other
forms
of
bias.
Thus,
we
recommend
as
the
most
desirable
form
of
CV
elicitation
the
use
of
a
dichotomous
question
that
asks
respondents
to
vote
for
or
against
a
particular
level
of
taxation,
as
occurs
with
most
real
referenda.
As
already
noted,
such
a
question
form
also
has
advantage
in
terms
of
incentive
compatibility.
(
If
a
doublebounded
dichotomous
choice
or
some
other
question
form
is
used
in
order
to
obtain
more
information
per
respondent,
experiments
should
be
developed
to
investigate
biases
that
may
be
introduced.)

0
Accurate
Description
of
the
Program
or
Policy:
Adequate
54
information
must
be
provided
to
respondents
about
the
environmental
program
that
is
offered.
It
must
be
defined
in
a
way
that
is
relevant
to
damage
assessment.

Ideally
a
CV
survey
would
elicit
attitudes
toward
three
alternative
(
future)
recovery
scenarios:
(
A)
"
immediate"

restoration,
(
b)
accelerated
restoration,
and
(
c)
natural
restoration.
Damages
would
be
the
difference
between
(
a)
and
(
b)

on
the
assumption
that
accelerated
restoration
is
provided
by
the
responsible
party.
Unfortunately,
respondents
may
not
find
"
immediate"
restoration
very
plausible
and
they
may
resist
the
notion
that
they
should
be
expected
to
contribute
to
accelerated
restoration
when
it
is
an
oil
company
that
is
at
fault.
If
respondents
are
unable
or
unwilling
to
deal
hypothetically
with
the
most
relevant
"
clean­
up"
scenarios,
alternative
"
prevention"

scenarios
will
have
to
be
used
in
the
survey
instrument.
For
example,
respondents
may
be
asked
to
vote
for
a
referendum
that
offers
reduced
risk
of
another
spill
for
a
specified
period
of
time.
3
The
weaker
is
the
linkage
between
the
"
prevention"

scenarios
and
the
"
clean­
up"
scenarios,
the
more
unreliable
are
the
survey
results.
Rhetorically:
Is
a
decade
of
prevention
equal
in
value
to
the
difference
in
value
between
accelerated
and
immediate
clean­
up?

3
As
in
the
survey
actually
performed
by
the
State
of
Alaska
after
the
Valdez
spill
(
See
Carson
et
al.
(
1992)).
55
0
Pretesting
of
Photographs:
The
effects
of
photographs
on
subjects
must
be
carefully
explored.

One
effective
means
for
conveying
information
and
holding
interest
in
a
CV
interview
has
been
the
use
of
large
and
impressive
photographs.
However,
this
technique
is
a
two­
edged
sword
because
the
dramatic
nature
of
a
photograph
may
have
much
more
emotional
impact
than
the
rest
of
the
questionnaire.
Thus
it
is
important
that
photographs
be
subjected
to
even
more
careful
assessment
than
verbal
material
if
the
goal
is
to
avoid
bias
in
presentation.
4
0
Reminder
of
Undamaged
Substitute
Commodities:
Respondents
must
be
reminded
of
substitute
commodities,
such
as
other
comparable
natural
resources
or
the
future
state
of
the
same
natural
resource.
This
reminder
should
be
introduced
forcefully
and
directly
prior
to
the
main
valuation
question
to
assure
that
respondents
have
the
alternatives
clearly
in
mind.

0
Adequate
Time
Lapse
from
the
Accident:
The
survey
must
be
conducted
at
a
time
sufficiently
distant
from
the
date
of
the
environmental
insult
that
respondents
regard
the
scenario
of
complete
restoration
as
plausible.
Questions
4
Failure
to
test
the
effects
of
photographs
on
responses
is
one
shortcoming
of
Carson
et
al.
(
1992).
56
should
be
included
to
determine
the
state
of
subjects'

beliefs
regarding
restoration
probabilities.

Survey
respondents
who
would
not
suffer
interim
passive­
use
loss
may
not
regard
full
restoration
as
very
plausible;

therefore,
they
may
report
substantial
passive­
use
loss
even
if
told
that
full
restoration
in
some
reasonable
amount
if
time
is
certain.
Misunderstanding
of
the
restoration
probability
is
most
acute
when
the
accident
has
recently
occurred
and
before
any
substantial
restoration
takes
place.
It
would
be
ideal
to
assess
steady
state
passive­
use
loss
after
natural
and
human
restoration
is
complete
or
nearly
so,
since
then
presumably
respondents
would
believe
in
the
restoration.
If
that
is
not
a
possibility,

surveys
might
be
conducted
over
time
until
the
reported
willingness
to
pay
settles
down
(
assuming
that
it
does),
as
the
respondents
come
to
believe
more
and
more
in
the
probable
success
of
the
restoration
effort.
Alternatively,
respondents
might
be
asked
to
value
a
menu
of
alternative
possible
scenarios,
without
being
told
explicitly
which
is
applicable
for
the
environmental
insult
under
study.
The
menu
should
be
designed
to
force
them
to
consider
the
difference
between
interim
and
steady­
state
passiveuse
value.

0
Temporal
Averaging:
Time
dependent
measurement
noise
should
be
reduced
by
averaging
across
independently
drawn
samples
taken
at
different
points
in
time.
A
clear
and
substantial
57
time
trend
in
the
responses
would
cast
doubt
on
the
"
reliability"
of
the
finding.

0
"
No­
answer"
Option:
A
"
no­
answer"
option
should
be
explicitly
allowed
in
addition
to
the
"
yes"
and
"
no"
vote
options
on
the
main
valuation
(
referendum)
question.

Respondents
who
choose
the
"
no­
answer"
option
should
be
asked
nondirectively
to
explain
their
choice.
Answers
should
be
carefully
coded
to
show
the
types
of
responses,

for
example:
(
i)
rough
indifference
between
a
yes
and
a
no
vote;
(
ii)
inability
to
make
a
decision
without
more
time
or
more
information;
(
iii)
preference
for
some
other
mechanism
for
making
this
decision;
and
(
iv)
bored
by
this
survey
and
anxious
to
end
it
as
quickly
as
possible.

0
Yes/
no
Follow­
ups:
Yes
and
no
responses
should
be
followed
up
by
the
open­
ended
question:
"
Why
did
you
vote
yes/
no?"

Answers
should
be
carefully
coded
to
show
the
types
of
responses,
for
example:
(
i)
It
is
(
or
isn't)
worth
it;
(
ii)

Don't
know;
or
(
iii)
The
oil
companies
should
pay.

0
Cross­
tabulations:
The
survey
should
include
a
variety
of
other
questions
that
help
to
interpret
the
responses
to
the
primary
valuation
question.
The
final
report
should
include
summaries
of
willingness
to
pay
broken
down
by
these
categories.
Among
the
items
that
would
be
helpful
in
58
interpreting
the
responses
are:

Income
Prior
Knowledge
of
the
Site
Prior
Interest
in
the
Site
(
Visitation
Rates)

Attitudes
Toward
the
Environment
Attitudes
Toward
Big
Business
Distance
to
the
Site
Understanding
of
the
Task
Belief
in
the
Scenarios
Ability/
Willingness
to
Perform
the
Task
We
believe
that
these
cross
tabulations
will
prove
useful
in
interpreting
and
lending
credibility
to
the
responses
and
possibly
also
in
forming
adjustments
that
can
enhance
reliability.

0
Checks
on
Understanding
and
Acceptance:
The
above
guidelines
must
be
satisfied
without
making
the
instrument
so
complex
that
it
poses
tasks
that
are
beyond
the
ability
or
interest
level
of
many
participants.

Since
CV
interviews
often
present
information
that
is
new
to
respondents,
the
questionnaire
should
attempt
at
the
end
to
determine
the
degree
to
which
respondents
accept
as
true
the
descriptions
given
and
assertions
made
prior
to
the
valuation
question.
Such
an
inquiry
should
be
carried
out
in
detail
but
59
non­
directively,
so
that
respondents
feel
free
to
reject
any
part
of
the
information
they
were
given
at
earlier
points.

GOALS
FOR
VALUE
ELICITATION
SURVEYS
The
following
items
are
not
adequately
addressed
by
even
the
best
CV
surveys.
In
the
opinion
of
the
Panel,
these
issues
will
need
to
be
convincingly
dealt
with
in
order
to
assure
the
reliability
of
the
estimates.

0
Alternative
Expenditure
Possibilities:
Respondents
must
be
reminded
that
their
willingness
to
pay
for
the
environmental
program
in
question
would
reduce
their
expenditures
for
private
goods
or
other
public
goods.
This
reminder
should
be
more
than
perfunctory,
but
less
than
overwhelming.
The
goal
is
to
induce
respondents
to
keep
in
mind
other
likely
expenditures,
including
those
on
other
environmental
goods,

when
evaluating
the
main
scenario.

Consumers
can
be
expected
to
make
expenditure
decisions
that
are
adequately
sensitive
to
other
expenditure
possibilities
with
which
they
are
familiar.
But
environmental
referenda
of
the
type
presented
in
CV
surveys
are
unfamiliar
and
respondents
may
not
be
aware
of
the
large
set
of
other
expenditure
possibilities
that
might
be
offered
in
future
CV
surveys
or
future
referenda.

Unless
informed
otherwise,
respondents
may
suppose
that
there
is
60
only
one
environmental
scenario
that
will
ever
be
offered
and
they
may
overspend
on
it.

It
is
not
at
all
clear
how
exhaustive
should
be
the
list
of
alternative
public
goods
that
are
explicitly
presented.
If
the
list
is
too
brief,
overspending
can
be
expected.
If
the
list
is
too
long,
respondents
will
be
encouraged
to
spread
expenditures
to
public
goods
for
which
there
is
not
adequate
total
demand
and
which
therefore
cannot
really
be
offered
to
them.
Also,
if
the
list
gets
large
enough
to
encompass
a
significant
fraction
of
income,
the
gap
between
willingness
to
pay
and
willingness
to
accept
may
widen.

It
is
also
not
clear
what
form
the
reminder
should
take.
It
does
not
seem
enough
merely
to
list
other
environmental
goods
since
respondents
would
then
have
to
guess
the
level
of
expenditure
that
would
be
necessary
to
pay
for
the
alternatives.

The
survey
should
probably
include
some
statement
about
the
price
of
the
alternatives,
for
example,
the
per
capita
expenditure
that
would
be
required
to
provide
the
items.

0
Deflection
of
Transaction
Value:
The
survey
should
be
designed
to
deflect
the
general
"
warm­
glow"
of
giving
or
the
dislike
of
"
big
business"
away
from
the
specific
environmental
program
that
is
being
evaluated.
It
is
possible
that
the
referendum
format
limits
the
"
warm
glow"

effect,
but
until
this
is
clear
the
survey
design
should
explicitly
address
this
problem.
61
Economic
models
of
consumer
behavior
generally
are
based
on
the
assumption
that
value
derives
from
the
goods
and
services
that
are
consumed,
not
from
the
process
by
which
these
goods
are
allocated.
But
happiness
that
derives
from
charitable
giving
may
come
mostly
from
the
act
of
giving
rather
from
the
material
changes
that
follow
from
the
gift.
To
give
another
example,

consumers
may
get
pleasure
from
the
act
of
shopping
as
well
as
from
ownership
of
the
goods
they
purchase.
Words
that
might
be
useful
to
distinguish
between
these
utility­
producing
events
are
"
consumption
value"
and
"
transaction
value,"
the
latter
referring
to
the
process
or
transaction
that
establishes
ownership.

We
do
not
question
the
validity
of
"
transaction
value"
or
differentiate
it
from
"
consumption
value"
as
far
as
damage
assessment
is
concerned.
But
for
both
forms
of
value,

respondents
need
to
be
thinking
clearly
about
the
substitutes,

since
the
closer
are
the
substitutes
the
less
the
damage
that
is
done.
In
the
case
of
"
transaction
value,"
there
are
many
close
substitutes
to
cleaning
up
oil
spills
since
there
are
many
other
charitable
activities
that
can
generate
the
same
"
warm
glow"
and
there
are
many
other
ways
to
express
hostility
toward
big
business
and
modern
technology.

0
Steady
State
or
Interim
Losses:
It
should
be
made
apparent
that
respondents
can
distinguish
interim
from
steady­
state
62
losses.

The
quality
of
any
natural
resource
varies
daily
and
seasonally
around
some
"
equilibrium"
or
"
steady
state"
level.

Active­
use
value
of
a
resource
depends
on
its
actual
state
at
the
time
of
use
(
and
at
other
times),
not
on
its
equilibrium.
But
passive­
use
value
of
a
natural
resource
may
derive
only
or
mostly
from
its
steady
state
and
not
from
its
day­
to­
day
state.
If
so,

full
restoration
at
some
future
date
eliminates
or
greatly
reduces
passive­
use
loss.
Surveys
accordingly
need
to
be
carefully
designed
to
allow
respondents
to
differentiate
interim
from
steady
state
passive­
use
loss.

0
Present
Value
Calculations
of
Interim
Losses:
It
should
be
demonstrated
that,
in
revealing
values,
respondents
are
adequately
sensitive
to
the
timing
of
the
restoration
process.

As
discussed
in
Section
III
above,
the
time
profile
of
restoration
following
an
accident
potentially
is
an
important
determinant
of
active­
use
loss
and
interim
passive­
use
loss,
but
respondents
may
have
little
ability
to
distinguish
between
and
to
evaluate
different
profiles.

0
Advance
Approval:
Since
the
design
of
the
CV
survey
can
have
a
substantial
effect
on
the
responses,
it
is
desirable
63
that
­­
if
possible
­­
critical
features
be
preapproved
by
both
sides
in
a
legal
action,
with
arbitration
and/
or
experiments
used
when
disagreements
cannot
be
resolved
by
the
parties
themselves.

0
Burden
of
Proof:
Until
such
time
as
there
is
a
set
of
reliable
reference
surveys,
the
burden
of
proof
of
reliability
must
rest
on
the
survey
designers.
They
must
show
through
pretesting
or
other
experiments
that
their
survey
does
not
suffer
from
the
problems
that
these
guidelines
are
intended
to
avoid.
Specifically,
if
a
CV
survey
suffered
from
any
of
the
following
maladies,
we
would
judge
its
findings
"
unreliable":

­­
A
high
nonresponse
rate
to
the
entire
survey
instrument
or
to
the
valuation
question.

­­
Inadequate
responsiveness
to
the
scope
of
the
environmental
insult.

­­
Lack
of
understanding
of
the
task
by
the
respondents.

­­
Lack
of
belief
in
the
full
restoration
scenario.

­­
"
Yes"
or
"
no"
votes
on
the
hypothetical
referendum
that
are
not
followed
up
or
explained
by
making
reference
to
64
the
cost
and/
or
the
value
of
the
program.

0
Reliable
Reference
Surveys:
In
order
to
alleviate
this
heavy
burden
of
proof,
we
strongly
urge
the
government
to
undertake
the
task
of
creating
a
set
of
reliable
reference
surveys
that
can
be
used
to
interpret
the
guidelines
and
also
to
calibrate
surveys
that
do
not
fully
meet
the
conditions.
65
Table
of
References
Andreoni,
James;
"
Giving
With
Impure
Altruism:
Applications
to
Charity
and
Ricardian
Equivalence;"
Journal
of
Political
Economy
97
(
1989);
pp.
1447­
1458.

Bishop,
Richard
C.,
and
Thomas
A.
Heberlien;
"
Measuring
Values
of
Extra­
Market
Goods:
Are
Indirect
Measures
Biased?"
American
Journal
of
Agricultural
Economics
61
(
1979);
926­
930.

Carson,
Richard
T,
Robert
Cameron
Mitchell,
W.
Michael
Hanemann,
Raymond
J.
Kopp,
Stanley
Presser,
and
Paul
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