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EFFECTS OF SCHEDULED OVERTIME ON LABOR PRODUCTIVITY

By H. Randolph Thomas,1 Member, ASCE

1Prof., Penn. Transp. Inst., Penn. State Univ., Res. Bldg. B, University
Park, PA 16802.

Note. Discussion open until August 1, 1992. To extend the closing date
one month, a written request must be filed with the ASCE Manager of
Journals. The manuscript for this paper was submitted for review and
possible publication on January 11, 1991. this paper is part of the
Journal of Construction Engineering and Management, Vol ' 118, No. 1,
March, 1992. (DASCE, ISSN 0733-9364/92/0001-0060/$1.00 + $.15 per page.
Paper No. 1241.

ABSTRACT: This paper reviews the construction literature on the effects
on labor productivity of scheduled overtime. The literature is organized
into three groups: studies based on data front project records, studies
in which the sources of data are unknown, and studies done in the
manufacturing sector. Analyses are also performed on the influence of
the number of days per week and the number of hours per day. The
literature on scheduled overtime was found to be very sparse; dated to
the late 1960s and earlier; based on small sample sizes; and largely
developed from questionable or unknown sources. The analysis reveals
very few original data. Many studies reference other studies, giving the
false appearance of originality. The analysis of data shows general
consistency with respect to overall losses of efficiency. However, with
respect to the loss of efficiency as a function of the number of hours
per day and the number of days per week, many studies show that the
effect of these two variables is negligible. The paper concludes that
these studies provide strange and largely unbelievable results.

INTRODUCTION

Construction overtime has frequently been used as in inducement to
attract labor and to accelerate schedule performance. Although there may
be positive short-term benefits to working an overtime schedule, the
long-term consequences are typically viewed as detrimental Understanding
the effects of overtime scheduling is quite difficult because the
factors affecting productivity in the overtime situation are numerous.
Furthermore, if an overtime schedule must be used, there is little, if
any, information available to aid in deciding which type of schedule to
adopt (Thomas 1990).

Reliable studies of the effects of extended overtime on labor
productivity are very difficult to produce because there are many
factors that can affect productivity, some of which have nothing to do
with the overtime situation. Examples include the character of work
being performed and start-up and testing activities. While obvious, it
is often forgotten that manpower is not the only resource or component
that is consumed at an accelerated pace in an overtime situation.
Materials are installed at a faster rate; consumables, tools, and
construction equipment are in greater demand; and engineering questions
and information demands must be processed at a faster rate. Absenteeism,
accidents, and fatigue may become a growing problem, and the quality of
workmanship may decline. Thus, if a project is behind schedule, working
overtime may simply exacerbate the problem. Therefore, whenever overtime
is discussed, the surrounding circumstances must be clearly understood.

OBJECTIVE

The objective of this paper is to critique the literature describing the
effects of an overtime schedule on construction-labor productivity. The
need for such a summary arises because, relative to the amount of
published literature, little is known about the origin of the overtime
data, number and type of projects, and surrounding circumstances. Yet
widespread assumptions have been made that the data and conclusions are
reliable. This paper clarifies the aforementioned aspects for each data
set.

SCOPE

This paper focuses on scheduled or extended overtime, that is, an
overtime schedule that lasts longer than several weeks. Spot overtime,
which is intermittent, is not covered, because the negative aspects are
minor relative to the job as a whole.

The literature was collected from published and unpublished sources. The
graphs are presented to illustrate the flaws in the data and should not
be interpreted as validating or invalidating the effects of scheduled
overtime on labor productivity.

DEFINITIONS

In this paper, the following definitions are used:

"Extended overtime" is involved in a work schedule that extends over
more than 40 hr of work per week. The schedule is planned in advance and
lasts for at least three consecutive weeks, and typically longer. The
term "overtime" is used interchangeably with "extended overtime."

"Labor productivity" is the ratio of the input in terms of labor hours
to the output in terms of units of work.

STUDIES OF HOURS PER WEEK AND HOURS PER DAY

Various studies have reported losses of productivity caused by scheduled
overtime. These studies are grouped in the following according to the
source of the data and the applicability to construction situations.

Data from Project Records

An extensive review of the published literature and other sources
yielded three studies of the effects of construction overtime in which
the project records were the basis for the conclusions. Table 1
summarizes pertinent data about each study.

 

Proctor & Gamble

The most publicized study of construction overtime is that made by
Proctor & Gamble at their Green Bay, Wisconsin, operation. The study was
first published as a Business Roundtable (BRT) report ("Effect" 1974)
and was reissued in 1980 as part of the Construction Industry Cost
Effectiveness Project ("Scheduled" 1980). Figs. 1 and 2 show the
reported effect on productivity of extended overtime for a period of 12
weeks. As stated in both reports, the figures represent "the reduction
in productivity normally experienced on projects operated on a basis of
50 hours per week and 60 hours per week….These observations are on a
weekly basis with all completed work recorded from physical count or
measurement and the work hours expended obtained from actual payroll
hours. The curves reflect the averages of many observations"
[("Scheduled" 1980) page 10].

The data in Figs. 1 and 2 are based on a comparison of actual work hours
expended to a fixed standard base called a "bogey." The "bogey" standard
is for a straight-time schedule. Unfortunately, the data are not a
comparison between actual productivity on straight time and overtime
productivity. The 1974 and 1980 reports contain the following warning
with respect to comparisons of various data sets: "Direct comparisons of
various data are difficult since all measurement of productive effort is
not referenced to a Fixed Standard. The Industrial firm's data on
productivity is based on Fixed Standards and a performance of 1.0 may
not be the same as a performance of 1.0 referenced to some other
standard of comparison. As a result, a 30% reduction of productivity in
one set of data could compare with a 15% reduction reflected in another
set of data due to this difference" [("Scheduled" 1980) page 15].

What is little known about the Business Roundtable reports is that the
data all originated from a single project (i.e., Proctor & Gamble's
Green Bay operation). Also, the nature of the Green Bay construction
activities is not known. The curves are a composite view of a series of
comparably short jobs on scheduled overtime covering a 10-year period.
The project operations were carried out in a tranquil labor climate and
the field management was reported to be excellent.

 

 

Foster Wheeler

A technical paper by L. V. O'Connor described the experiences of Foster
Wheeler in constructing five large fossil boilers in the Ohio Valley
between 1963 and 1968 (O'Connor 1969). The curve in Fig. 3 shows the
results. The paper reported an average productivity decline of 7.9% per
year during the period because of a variety of factors, including
overtime, over-manning, and labor strikes. Although it is not explicitly
stated, the reader is left with the impression that the conclusions are
based on the boilermaker craft. No other information is given, and it is
not known how the overall trend of productivity losses form the other
causes was factored into Fig.3. The percentage loss of efficiency is
consistent with the BRT report if the scheduled overtime period is about
five to six weeks.

 

Construction Industry Institute

In 1984, the Construction Industry Institute (CII) sponsored a
three-year study of construction overtime ("The Effects" 1988). This
study represents the only source of original data since the 1960s. The
study also differs from the previous two studies in several important
respects. The data base includes multiple projects, and the data were
collected by direct observation rather than from project records. The
focus is on the work of a single crew as opposed to an entire craft, and
the study reported results for a number of crafts. The analyses are
independent of the project estimate.

The study included seven projects. As shown in Table 2, the two natural
gas recovery projects were in the early stages of completion and the
refinery expansion project was nearing completion. One was a shutdown
project, and another (project 4) was experiencing considerable
productivity problems aside from the overtime situation. Project 5 was
on a rolling 4/10 (four days of 10 hr each) schedule. Only on projects 3
and 4 were data collected on straight-time and overtime schedules.

 

The limitations of the study include the inability to compare overtime
productivity to straight-time productivity, incomplete data-collection
procedures, the use of moving-average calculations, and the inability to
correlate changes in productivity to other factors and job-site
conditions. The problems caused by these limitations are illustrated in
Figs. 4 and 5, which show the overtime and straight-time productivities
of electricians on project 4. No discernible patterns can be identified.
On project 3, the electrician productivity was better on a six-day, 10
hr schedule than on straight time.

The CII study could not develop defensible conclusions relative to the
effects of an overtime schedule, because the productivity trends for the
same crews were not consistent. The report did conclude that
productivity does not necessarily decrease on an overtime schedule. At
best, fatigue did not seem to be a factor.

 

Other Studies of Effects on Construction Productivity

Five other sources of information summarizing the effects of
construction overtime were identified in the literature. In each of
these, the source of the data is either unknown, is considered to be
more opinion than factual, or is a republication of other data. Table 3
summarizes these sources. As can be seen, most of this information is
also significantly dated.

 

National Electrical Contractors Association

In 1969, the National Electrical Contractors Association (NECA)
published the results of a 1964 study of overtime done by the NECA
Southeastern Michigan Chapter (Overtime 1969, 1989). The findings for
electricians for 50 hr and 60 hr worksheets showing productivity losses
as a function of the schedule used and the duration are presented in
Figs. 1 and 2. The origin of the data is unknown.

NECA also published the results of a survey of 289 NECA members
regarding their experiences with reduced productivity associated with
overtime (Overtime 1962). These data are generally consistent with the
Foster Wheeler data except for the 6/10 schedule. They are somewhat
consistent with the 1969 NECA Michigan Chapter study except for several
of the more demanding schedules.

C.F. Braun Inc.

Unpublished material from the C. F. Braun Inc. construction guide
(unpublished 1979) contains data that are remarkably similar to the
Foster Wheeler data and therefore raise doubts about their originality.
No information is available about the origin of the data.

J. J. Adrian

 F). The losses of productivity are shown in Fig. 6.

Qualified Contractor

Qualified Contractor (Howerton 1969) published statistics on an overtime
study conducted in 1964 [(Oglesby et al. 1989) page 260]. The data are
plotted in Fig. 7. As the figure illustrates, the data are similar to
those of Adrian (1987).

 

Mechanical Contractors Association of America

The Mechanical Contractors Association (MCA) provides information to its
membership in the form of management methods bulletins. Bulletin No. 18A
(dated January 1968) ("How" 1968) and Bulletin No. 20 (dated November
1968) ("Tables" 1968) were issued to assist contractors in the
preparation of claims and change orders relative to overtime
inefficiencies. Fig. 8 illustrates the losses that can be expected. As
noted, the data are based on U.S. Department of Labor Bulletin 917
(Kossoris 1947,i,b). As is indicated later, Bulletin 917 summarizes data
from the manufacturing sector, not from construction. Therefore, the MCA
bulletins ("How" 1968; "Tables"' 1968) do not contain original data.

 

American Subcontractors Association

The Associated General Contractors, the American Subcontractors
Association, and the Associated Specialty Contractors, Inc., jointly
published a primer on overtime (Owner's 1979). The data are identical to
those published by the Business Roundtable ("Effect" 1974; "Scheduled"
1980). Thus, the ASA primer contains no original data.

American Association of Cost Engineers

The American Association of Cost Engineers published a bulletin on
overtime ("Effects" 1973). The data are identical to those published by
the Business Roundtable ("Effects" 1974; "Scheduled" 1980). Therefore,
the AACE bulletin contains no original data.

STUDIES IN MANUFACTURING SECTOR

A cursory review of the literature of overtime effects in manufacturing
and other industries yielded very little quantitative information. The
most notable reference is Bureau of Labor Statistics (BLS) Bulletin 917,
published in 1947 (Kossoris 1947a,b). This report has been Mdely cited
as a reliable source relative to construction ("Effect" 1974;
"Scheduled" 1980; Owiler's 1979; "How" 1968; "Tables" 1968).

The 1947 BLS study involved 2,445 men and 1,060 women and covered 78
case studies at 34 facilities in a wide variety of manufacturing
industries and settings such as foundries, machine shops, product
packaging, and assembly and production lines. Production products
included engines, airplanes, piston rings, metal bearings, airfield
landing mats, hats and clothing, rubber hoses, office supplies, and
cigars. Packaging activities included biochemicals, pharmaceuticals, and
cough drops. Most of the work was indoors, some was machine paced, and
most was highly repetitive. There were no construction activities
included in the study.

The results of the study showed that efficiency was impaired as the work
schedule exceeded 40 hr/week. The average efficiency for 50 hr, 60 hr,
and 70 hr weeks was 0.92, 0.84, and 0.78, respectively. The degree of
inefficiency was affected by the work schedule, the physical exertion
required, and the pace of the machine. Comparisons to prewar situations
in which the same work schedule was used were possible in 15 cases. The
study found that efficiencies were better in all cases during the
wartime period. The gain in efficiency ranged from 0.7% to 29.0%. The
average gain was 13.6%. Thus, it appears that patriotism was a
significant variable, and that the study results may not be applicable
to other situations.

ANALYSIS OF HOURS PER DAY

Aside from determining the hours per week to be worked, one must also
decide on the number of work hours per day. Common sense dictates that
the rate of loss efficiency should accelerate nonlinearly as the length
of the workday increases and as the number of hours per week increases.

Figs. 9-12 show the reported loss of efficiency as a function of the
length of the workday and the number of hours per week. These figures
provide somewhat conflicting and irregular results. Fig. 9 shows
patterns that would be expected, although some might expect the
differential between the 10 hr and 12 hr days to be greater. In Fig. 9,
the differences appear to be almost linear. However, Figs. 10-12 show
that the loss of efficiency is not related to the hours worked per day.
In fact, Adrian's (1987) data show that in some ranges the longer
workday is more efficient. Thus, the curves in Figs. 11 and 12 do not
seem consistent with expectations.

 

 

 

SYNOPSIS

The literature review reveals very little original data relative to
construction overtime activities. Except for the CI I ("The Effects"
1988) and Adrian (1987) studies, all of the data originate from the
1960s or earlier. Very little is known about how the data were collected
or the conditions under which the work was performed. Fig. 13 shows the
reported efficiency for various 50 hr, 60 hr, and 70 hr workweeks. The
basis for comparison is a 10 hr workday.

The results are generally consistent in that there is about a 10%
increase in efficiency losses for each additional 10 hr per week added
to the schedule beyond 40 hr. However, the conclusions that can be drawn
from these data are somewhat uncertain, especially for the longer
schedules.

Figs. 1 and 2 show the change in efficiency as a function of time for 50
hr/week and 60 hr/week schedules. The findings are generally consistent,
although there is very little data on which to base conclusions.

The literature is inconsistent relative to the loss of efficiency as a
function of the length of the workday. In one instance, the decrease in
efficiency loss appears linearly related to the length of the workday;
whereas in three other instances, loss of efficiency appears to be
unrelated.

STUDIES OF DAYS PER WEEK

An increase in the number of hours worked can be made by increasing the
hours worked per day, the number of days worked per week, or both.

Considerable uncertainty exists as to which is the most effective work
schedule, although there is research to support the notion that workers
need at least one day per week to relax (Kossoris 1947a,b).

Five-, Six-, and Seven-Day Workweeks

Common sense suggests that the longer the workweek and the more days per
week, the greater the inefficiencies. The daily inefficiencies of
starting up and winding down have been noted in other literature.
Therefore, in choosing between two overtime schedules, both with the
same number of hours per week, the better choice should logically be the
one with the fewest days per week.

A number of the studies addressed the inefficiencies of working five
days or more per week. These can be grouped into three general
categories. The first category are those showing the expected trend of
greater inefficiencies as the schedule extends to six and seven
workdays. Fig. 14 shows the data from the NECA study (Overtime 1969).
Using a 60 hr week as the basis for comparison, it shows that the
seven-day schedule is about 7% less efficient than the six-day schedule.

 

The second category included data from the Foster Wheeler (O'Connor
1969), C. F. Braun Inc. (unpublished 1979), Adrian (1987), and Bureau of
Labor Statistics (Kossoris 1947a,b) studies. Fig. 3, from the Foster
Wheeler study, is typical; it shows that the number of days per week has
little influence on the efficiency of construction operations. Figs. 15
and 16 actually show that the five-day schedule is less efficient than
the six-day schedule when the number of hours worked per week is less
than 55.

In the third category, Fig. 17, from the 1969 NECA survey, shows the
longer workday schedules to be more efficient. The five-day schedule is
less efficient than the six-day schedule. The curve for the seven-day
schedule shows a 70 hr/week schedule to be more efficient than a 56 hr
schedule.

In reviewing these data, one can readily discard the NECA survey data
[(Overtime 1969) (Fig. 17)] as erroneous. While the results from the
second category cannot be discarded, they can also be viewed with some
degree of suspicion. Only Fig. 14 shows results that are consistent with
generally accepted expectations and knowledge in the construction
industry.

 

 

The Four-Day, 10 hr Schedule

The four-day, 10 hr/day schedule has gained popularity in the
construction industry. An extension to this schedule is the rolling 4/10
schedule, in which two work forces alternate; that is, each work force
is scheduled for four days on and three or four days off. In this way,
the project can be manned continuously.

Based on the experiences of Daniel International (McConnell 1982), the
4/10 schedule has the following advantages.

 	The option to make up rain-out days on Friday, thus avoiding the
expense of weekend work schedules.

The disadvantages of the 4/10 schedule are the following.

 	Owner personnel may have to adjust the normal work schedule.

Two studies have cited certain advantages and disadvantages of the 4/10
schedule in quantitative and qualitative terms. These are as follows.

First, an in-house study by Daniel International (The Four- Ten 1979
based on 10 years of experience with the 4/10 schedule, concluded that
the 4/10 schedule was superior to other schedules. This conclusion
resulted from both quantitative and qualitative analyses.

The quantitative analysis was a 20-week work-sampling study at a test
site in the southeastern United States during the period from November
1975 to mid-March 1977. During this time, two schedules were used: a
4/10 and a 5/8. The work-sampling results are summarized in Table 4.

 

The study also examined the level of activity during the beginning and
end of the shift. The percentage of direct activity during the first and
eighth hours on the 5/8 schedule was no different than the ninth and
tenth hours on the 4/10 schedule. While direct work activity is not well
correlated to labor productivity (Thomas 1991), it would appear that
differences in the level of activity on the site as a function of the
schedule are insignificant.

Second, as part of the overtime study by CII ("The Effects" 1988), one
project in the study used a rolling 4/10 schedule. The project was the
construction of a chemical processing unit. Data were collected on crews
installing pipe, conduit, tubing, terminations, cables, wire, and
feeders.

The study made no comparison between the 4/10 schedule and any other.
The results showed that during the seven-month duration of the study,
the general productivity trend for all of the crews did not change,
although there were brief periods of improvement and deterioration. The
report made no assessment of the efficiency of the 4/10 schedule
compared to other schedule alternatives.

Synopsis

Overall, the studies of different work schedules are inconclusive as to
which alternative schedule is most efficient. Several studies show that
a shorter workweek is best; and one study shows that longer workweeks
are preferable. However, most studies show very little difference.

With respect to the 4/10 schedule, only one source was identified.
Daniel International (The Four- Ten 1979) concluded that the 4/10
schedule was more efficient than a normal schedule of five 8 hr days.

CONCLUSIONS

The literature on scheduled overtime was found to be very sparse; dated
to the late 1960s and earlier; based on small sample sizes; and largely
developed from questionable or unknown sources. Although there appears
to be a number of data sources, this is an illusion because many of the
articles and publications quote other sources while providing no new
data or insight. Where the data source is known, other pertinent
information, such as the environmental and site conditions, quality of
management and supervision, and labor situation, is unknown. The various
graphs and data that have been published are inherently unreliable,
except perhaps to suggest an upper bound on the losses of efficiency
that might be expected. The literature offers no guidance as to what
circumstances may lead to losses of efficiency.

With respect to the loss of efficiency as a function of the number of
hours per day and the number of days per week, the literature provides
strange and largely unbelievable results. The results from the
southeastern Michigan NECA study (Overtime 1969) and as reported in
Qualified Contractor (Howerton 1969) both show losses of efficiency as
the length of the workday increases and as more days per week are
worked. These data suggest that the six-day week is about 7% (absolute)
more efficient than the seven-day week. The 10 hr workday compared to a
9 hr workday results in a loss of efficiency of about 4% (absolute). The
12 hr day results in a loss of efficiency of another 7-8% (absolute).

The studies by Foster Wheeler, C. F. Braun Inc., Adrian, the Bureau of
Labor Statistics, and the Southeastern Michigan NECA survey show that
efficiency is not related to the number of work hours per day or the
number of workdays per week. Since it is not possible to increase the
total hours per week in any other way, it is concluded that these
studies are flawed.

ACKNOWLEDGMENT

This paper is based on research sponsored by the Construction Industry
Institute (CII). The support of the Overtime Task Force is gratefully
appreciated.

APPENDIX. REFERENCES

Adrian, J. J. (1987). Construction productivity improvement. Elsevier
Science Publishing Co., New York, N.Y.

"Effects of scheduled overtime on construction projects." (1973).
Report, American Association of Cost Engineers, Morgantown, W.Va.

"Effect of scheduled overtime on construction projects." (1974). Coming
to grills with some major problems in the construction industry,
Business Roundtable, New York, N.Y., 1-14.

Howerton, J. (1969). "Do you know the hidden costs of overtime'?"
Qualified Contractor, (Mar.).

"How much does overtime really cost." (1968). Bulletin No. 18A,
Mechanical Contractors Association of America, Washington, D.C.

Kossoris, M. (1947a). "Studies of the effects of the long working
hours." Bulletin 917, Bureau of Labor Statistics, Washington, D.C.

Kossoris, M. (1947b). "Studies of the effects of the long working
hours." Bulletin 917A, Bureau of Labor Statistics, Washington, D.C.

McConnell, G. (1982). "Evaluation of six alternative work schedules."
Fluor-Daniel Construction Co., Inc., Greenville, S.C.

O'Connor, L. V. (1969). "Overcoming the problems of construction
scheduling on large central station boilers." Proc., American Power
Conf., (31), 518-528.

Oglesby, C., Parker, H., and Howell, G. (1989). Productivity improvement
in construction. McGraw-Hill Book Co., Inc., New York, N.Y.

Overtime and productivity in electrical construction. (1969). National
Electrical Contractors Association, Washington, D.C.

Overtime and productivity in electrical construction, 2nd Ed. (1989).
National Electrical Contractors Association, Bethesda, Md.

Overtime work efficiency survey. (1962). National Electrical Contractor
Association, Washington, D.C.

Owner's guide on overtime, construction costs and productivity. (1979).
American Subcontractors Association, Association General Contractors of
America, and Associated Specialty Contractors, Inc., Washington, D.C.

"Scheduled overtime effect on construction projects." (1980).
Construction Industry Cost Effectiveness Task Force Report C-2, Business
Roundtable, New York, N.Y. "Tables for calculation of premium time and
inefficiency on overtime work." (1968). Bulletin No. 20, Mechanical
Contractors Association of America, Washington, D. C.

"The effects of scheduled overtime and shift schedule on construction
craft productivity." (1988). Source Document 43, Construction Industry
Institute, Austin, Tex. 'The four-ten hourlday work week. (1979). Daniel
International Construction Company ' Inc., Greenville, S.C.

Thomas, H. R. (1990). "Effects of scheduled overtime on labor
productivity: A literature review and analysis." PTI Report No. 9107,
The Pennsylvania State University, University Park, Pa.

Thomas, H. R. (1991). "Labor productivity and work sampling: The bottom
line." J. Constr. Engrg. and Mgmt., ASCE, 117(3), 423-444.

