The Analysis and Valuation of Disruption

The Analysis and
Valuation of Disruption

by Derek Nelson,
Senior Vice President & Regional Managing Director – Asia
Hill International, Inc

25 January 2011

The Analysis and Valuation of Disruption

Table of Contents

Introduction 3
What is Disruption? 3
What is Productivity? 4
Why is Productivity Important? 4
Background 5
Factors Affecting Labour Productivity 5
Project Change 7
Extent of Project Change 8
Disruptions and Cumulative Impacts 9
Methods of Quantifying Lost Productivity 10
Project Practice Based Methods 13
Measured Mile Analysis 13
Baseline Productivity Analysis 16
System Dynamics Modelling 17
Earned Value Analysis 22
Sampling Methods 23
Comparison Studies 24
Industry‐Based Methods 24
Cost‐Based Methods 24
Other Quantifying Methods 25
Matching the Quantifying Methods with Project Practice 26
Conclusions 27
Attachment 31

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Introduction

Complaints of ‘disruption’ and additional costs are routinely made during the course of a construction
project yet they remain notoriously difficult to prove.

One of the main reasons for this is that productivity losses are often difficult to identify and distinguish
at the time they arise, as opposed to other money claims which are more directly concerned with the
occurrence of a distinct and compensable event together with a distinct and direct consequence, such
as an instruction for a discreet variation during the progress of the works or a properly notified
compensation event.

As such, most claims for disruption are dealt with retrospectively and the claimant is forced to rely on
contemporary records to try and establish a causal nexus for identified losses (cause and effect) which
are all too often inadequate for the purposes of sufficiently evidencing a loss of productivity claim.
When this happens the claimant is often forced into the situation where it advances a weak global or
total cost claim of sorts to try and recover some of its losses.

The cause and effect burden of proof is the same for a claim for loss of productivity as for any other
claim insofar as the claiming party must first establish that the event or factor causing the disruption is a
compensable risk event under the contract. To do this, the contract needs to be reviewed to
understand the basis of the agreement as certain productivity issues may have been foreseeable and
therefore accounted for within the claimant’s productivity allowances.  The contract may also identify if
a party expressly accepted certain productivity risks.

Where courts and tribunals have a clear focus on linking cause and effect, claims for disruption will
come under greater scrutiny.  It is unlikely that contractors and subcontractors will succeed where their
claims for disruption are based simply on a global overspend on labour or plant for the whole of the
contract working period.  Sufficient detail is required to isolate the cause of the disruption complained
of and evaluate the effects of that disruption.

What is Disruption?

Disruption is loss of productivity, disturbance, hindrance or interruption to a Contractor’s normal
working methods, resulting in lower efficiency.  In the construction context, disrupted work is work that
is carried out less efficiently than it would have been, had it not been for the cause of the disruption.  If
caused by the Employer, it may give rise to a right to compensation either under the contract or as a
breach of contract.1

Construction contracts have two major types of costs associated with them: fixed and variable.

Fixed costs are those costs that the contractor procures on a fixed‐price subcontract or purchase order.
Fixed costs are inherently lower in risk, because the contractor has fixed them through a contract.  Risks
do exist, such as the financial failure or default of either a vendor or subcontractor or the installation of
defective or faulty work by a subcontractor or vendor, but the risks are much less than the risks in
variable‐cost items.

1
SCL Delay and Disruption Protocol: October 2002.

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Variable costs are items such as the contractor's labour, equipment, and site overhead. Extensive
literature has been published about delay claims, which principally are claims related to the extended
duration of the job and the resulting extended site overhead costs. However, the major variable risk
component on a construction project is labour, not extended site overhead. Equipment, on certain
types of construction such as utility, heavy, and highway construction, can be a significant cost;
however, equipment costs tend to be proportional to labour costs.  It is uncommon to have significant
increases in equipment costs without significant increases in labour costs.

On many construction projects, the largest single area of cost overrun is in labour costs. This is not
surprising given that labour is frequently the largest variable cost for a contractor.  Claims involving lost
productivity are frequently referred to as disruption claims.

What is Productivity?

Productivity   =   Production Output/Resource Input
=   4 m of 4” pipe/labour‐hour

Productivity Ratio   =   Actual Productivity/Planned Productivity
=   3 m per hr/4 m per hr
=   0.75

Why is Productivity Important?

Hypothetical Project Cost Components

Labour 40%  Often the largest cost
component;
 Most volatile cost
component
 Most critical cost to control
Materials 40%
General Conditions and Indirect Costs 10%
Overhead 5%
Profit 5%
Total 100%

Should the above project suffer a 12.5% overrun on the labour cost component:

Hypothetical Project Cost Components

Labour 40% → 45% Arising from a 12.5% overrun on
labour content
Materials 40%
General Conditions and Indirect Costs 10%
Overhead 5%
Profit 5% 0% A 12.5% overrun on labour content
Wipes out all profit on the project
Total 100%
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The existence of a labour cost overrun is not proof that an event entitling a contractor to damages has
occurred. Clearly labour cost overruns can occur for a variety of reasons, not all of which entitle a
contractor to compensation.
One of the most contentious areas in construction claims is the calculation or estimation of lost
productivity.  Unlike direct costs, lost productivity is often not tracked or cannot be discerned separately
and contemporaneously. As a result, both causation and entitlement concerning the recovery of lost
productivity can be difficult to satisfactorily establish.

Compounding this situation, there are numerous ways to calculate lost productivity and no uniform
agreement within the construction industry as to a preferred methodology of calculating lost
productivity. Many methods of calculation are open to challenge with respect to their validity and
applicability to particular cases, thus making settlement of the issue on a particular project potentially
problematic.2

Within the past 20 years, there has been significant research in construction labour productivity which
provides an increasing body of empirical data as to the effects of various factors on construction labour
productivity.  Some of the difficulties in applying that data to a specific project is outlined herein.

Background

Project changes, disruptions, cumulative impacts, and factors affecting labour productivity have strong
interrelationships.  They also play a vital role in establishing liability, causation, and resultant loss in lost
productivity claims. Change is one crucial factor in a range of factors influencing labour productivity.
The following is a brief discussion of these concepts.

Factors Affecting Labour Productivity

Labour productivity is a function of various controllable and uncontrollable factors. Schwartzkopf3
listed these factors under six groups comprising:
(1)   Schedule acceleration;
(2)   Change in work;
(3)   Management characteristics;
(4)   Project characteristics;
(5)   Labour and morale; and
(6)   Project location/external conditions.

2
Construction Industry Institute, An Analysis of the Methods for Measuring Construction Productivity, SD‐13, Austin, Texas,
1984.
3
Schwartzkopf, W. (1995). Calculating lost labor productivity in construction claims, Wiley, New York.
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Borcherding and Alarcon4 present a comprehensive review of quantitative information on factors
influencing productivity. In addition, they categorised the major components of productivity loss as
waiting or idle, travelling, working slowly, doing ineffective work, and doing rework.5

As noted previously, a number of factors may influence the actual productivity achieved on a given
project:

Figure: Example factors affecting productivity6

Clearly not all disruption attracts the payment of compensation. The contractor may be entitled to
compensation for the effects of lost productivity to the extent that a breach of obligation exists, a causal
link to the offending party can be established and the effects of that disruption calculated appropriately.
Most standard forms of contract do not deal expressly with disruption.  If they do not, then disruption
may be claimed as being a breach of the term generally implied into construction contracts, namely that
the Employer will not prevent or hinder the Contractor in the execution of its work. 7

4
Borcherding, J. D., and Alarcon, L. F. (1991). “Quantitative effects on productivity.” Constr. Lawyer, 11(1).
5
Specific factors and their descriptions are available in Borcherding, J. D., and Alarcon, L. F. (1991). “Quantitative effects on
productivity.” Constr. Lawyer, 11(1), Mechanical Contractors Association of America (MCAA) (1994). “Factors affecting labor
productivity.” Labor estimating manual, bulletin No. PD2, Rockville, Md., 1–3, Schwartzkopf, W. (1995). Calculating lost labor
productivity in construction claims, Wiley, New York, and Association for the Advancement of Cost Engineering (AACE)
International, Inc. (2004). “Estimating lost labor productivity in construction claims.” AACE International Recommended
Practice No. 25R‐03.
6
The figure presented is intended as illustrative only of the type of matters that may influence productivity on a given site.
Adapted from a presentation by Dr. Ibbs “Measuring Productivity for Improved Project Performance”, 2009.
7
SCL Delay and Disruption Protocol: October 2002.
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Project Change

Whilst a number of the factors impacting on labour productivity on a project are readily identifiable, the
consequences of change are often underestimated and therefore specifically referenced here.

Change is normally defined as any event that results in a modification of the original scope, execution
time, cost, and/or quality of work8.  There are generally five types of changes, namely:
 Change in scope;
 Differing site conditions;
 Delays;
 Suspensions; and
 Acceleration.

The costs of performing changed work consist of both:
(1) Those costs directly related to the accomplishment of the changed work; and
(2) Those costs arising from the interaction between the changed work and unchanged work9.

Notwithstanding that most forms of contract recognise and provide for the valuation of work relative to
the circumstances under which it is being executed, this second aspect is often significantly
underestimated or undervalued by both Contractors or Employers and their Representatives.

The costs and schedule impacts of a change occur in four phases:

Phase One is the time prior to the recognition of the change. An example would be a tradesman
determining that the plans do not fit the situation encountered. The tradesman first attempts to
determine if he is misreading the plans, then will seek direction from the supervisor who, if the
supervisor cannot resolve the problem, will then seek direction from the engineer or the owner.  After
some period of time, a clarification may be issued.  It may be determined that a change is necessary to
deal with the situation. During the period before a change is recognised, costs and delays can be
incurred. The process of finding a problem and implementing the solution is outlined in summary
below10.

8
Ibbs, C. W., and Allen, W. E. (1995). “Quantitative impacts of project change.”; Revay, S. O. (2003). “Coping with changes.”
AACE Int. Transactions, CDR.25, 1–7.
9
Triple “A”South, ASBCA No. 46866, 94‐3 BCA ¶27,194, at 135,523.
10
Developed from William Schwartzkopf, Calculating Lost Labour Productivity in Construction Claims, 2nd Edition, Aspen.
Page | 7


Attachment 1 presents a larger scale of the above process diagramme.

Phase Two occurs after the need to make a change is recognised. During this period, materials are
procured and the work is scheduled. Tradesmen may either be doing other work while waiting to
perform the change or working around the change.  Either of these actions can cause inefficiencies.

Phase Three is the actual execution of the changed work. The costs incurred during this phase are
generally referred to as the direct cost of the change.  These costs represent the time required and cost
to perform the changed work.

Phase Four represents the work performed after the changed work has been performed.  The cost and
schedule effects during this phase and the first phase are indirect and are often referred to as impact
costs. The amount of these impact costs is often the subject of considerable disagreement. By
comparison, the direct costs during the third phase can frequently be measured and, therefore, the cost
of the labour, materials, equipment, and other items can be determined. If a project is impacted by
multiple changes, it may be necessary to analyse the effect of all of the changes simultaneously because
of the interaction of the various changes.

Extent of Project Change

The degree of project change varies according to each project but can be significant. Among 24
construction projects in western Canada, project costs increased by at least 30% for more than half and
60% on a third of projects11.  Several projects suffered delays over 100%.  A study of the Joint Legislative
Audit and Review Commission12 on approximately 300 road construction projects in Virginia revealed
that the average financial project change was more than 11%.

The amount and timing of change are also significant factors affecting productivity. Analysis of 90
construction disputes in 57 independent projects13 showed that there was a significant direct correlation

11
Semple, C., Hartman, F. T., and Jergeas, G. (1994). “Construction claims and disputes: Causes and cost/time overruns.” J.
Constr. Eng. Manage., 120(4), 785–795.
12
Joint Legislative Audit and Review Commission (JLARC). (2001). “Review of construction costs and time schedules for Virginia
highway projects.” House Document No. 31, Commonwealth of Virginia.
13
Leonard, C. A. (1987). “The effect of change orders on productivity.” Revay Rep., 6(2), 1–4.
Page | 8


between the percentage of change order hours to contract hours and the percentage of lost
productivity.  Ibbs14 found that:
(1)   The greater the amount of change, the less the efficiency is; and
(2)   Late project change more adversely affects labour productivity than early change.

This finding was also confirmed by later studies15.

Disruptions and Cumulative Impacts

In Coastal Dry Dock & Repair Corp., disruption is noted as the “cost effect upon, or the increased cost of
performing, the unchanged work due to a change in contract”16. In some studies17, disruptions are
defined as the occurrence of events that are acknowledged to negatively impact on labour productivity.
More broadly, the AACE; Recommended Practice standard18 defines “disruptions as an action or event
which hinders a party from proceeding with the work or some portion of the work as planned or as
scheduled.”

As noted previously, disruptions can be caused by change. These changes can reduce labour
productivity and extend the project duration19.  Disruptions caused by change can be both foreseeable
and unforeseeable.  The foreseeable or local disruptions can occur at the same time and either the same
place or within the same resource as the changed work, whereas unforeseeable or cumulative
disruptions can also occur at a time or place, or within resources, different from the changed work20.
The words “cumulative disruption” and “cumulative impact” can be used interchangeably.

Cumulative impact has been described as being “…the unforeseeable disruption of productivity resulting
from the ‘synergistic’ effect of an undifferentiated group of changes.  Cumulative impact is referred to
as the ‘ripple effect’ of changes on unchanged work that causes a decrease in productivity and is not
analysed in terms of spatial or temporal relationships”21. Jones22 argued that when the Board states
that cumulative impact cannot be analysed in terms of spatial or temporal relationships, it means that
cumulative impact costs cannot be secured within individual contract changes.

Pricing of the direct impact due to local disruptions and cumulative impacts due to cumulative
disruptions is different.  The direct impact costs are prepared on a forward pricing basis.  The cumulative
impact costs, on the other hand, are more often priced on a backward pricing basis as a contractor
cannot foresee or readily quantify the impact.  In other words, a cumulative impact claim addresses the

14
Ibbs, C. W. (1997). “Quantitative impacts of project change: Size issues.” J. Constr. Eng. Manage., 123(3), 308–311, Ibbs, W.
(2005). “Impact of change’s timing on labor productivity.” J. Constr. Eng. Manage., 131(11), 1219–1223.
15
E.g., Hanna, A. S., Russell, J. S., Gotzion, T. W., and Nordheim, E. V. (1999). “Impact of change orders on labor efficiency for
mechanical construction.” J. Constr. Eng. Manage., 125(3), 176–184.
16
Coastal Dry Dock & Repair Corp., ASBCA No. 36754, 91‐1 BCA ¶23,324, at 116,989, 1990.
17
Thomas, H. R., and Napolitan, C. L. (1995). “Quantitative effects of construction changes on labor productivity.” J. Constr. Eng.
Manage., 121(3), 290–296.; Thomas, H. R., and Raynar, K. A. (1997). “Schedule overtime and labor productivity: Quantitative
analysis.” J. Constr. Eng. Manage., 123(2), 181–188.
18
Association for the Advancement of Cost Engineering (AACE) International, Inc. (2004). “Estimating lost labor productivity in
construction claims.” AACE International Recommended Practice No. 25R‐03.
19
Hanna, A. S., Lotfallah, W. B., and Lee, M. J. (2002). “Statistical‐fuzzy approach to quantify cumulative impact of change
orders.” J. Comput. Civ. Eng., 16(4), 252–258.
20
Finke, M. R. (1998). “A better way to estimate and mitigate disruption.” J. Constr. Eng. Manage., 124(6), 490–497.
21
Centex Bateson Construction Co., VABCA No. 4613, 99‐1 BCA ¶30,153, at 149,259, 1998.
22
Jones, R. M. (2001). “Lost productivity: Claims for cumulative impact of multiple change orders.” Public Contract Law J., 31(1),
1–46.
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changed work’s effect on working conditions that will indirectly influence the unchanged work, whereas
a direct impact claim covers the impact of changed work on unchanged work23.

The AACE Recommended Practice24 notes: “contractors tend to blame such losses on owners and ask to
be compensated.  Owners, on the other hand, often blame a bad bid or poor project management and
thus deny additional compensation for lost productivity. Given this situation the root cause of lost
productivity is frequently a matter in dispute between owners, contractors and subcontractors.”

This paper seeks to set out appropriate approaches and recognised practices designed to overcome
those inherent obstacles in analysing and quantifying the effects of such disruption.

Methods of Quantifying Lost Productivity

The construction industry has developed and employed a number of methodologies for estimating lost
labour productivity. Based on the appropriate data input, these methods can be classified into three
major groups; namely:
(1) Project practice based;
(2) Industry based; and
(3) Cost based methods.

The detailed data requirements and corresponding judicial acceptance generally increase as the
approach adopted moves from cost based to project practice based methods.

23
Jones, R. M. (2001). “Lost productivity: Claims for cumulative impact of multiple change orders.” Public Contract Law J., 31(1),
1–46.
24
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The above figure25 outlines the relationships between the availability, quality and providence of the
contemporaneous project documentation, the reliability of the methods of quantifying lost productivity
and the cost and expertise generally required to record, prepare, and document the quantum of
damages derived thereby.

The horizontal axis refers to the attributes of the project data.  The two vertical axes refer to attributes
of the methods available for calculating lost productivity.
The methods listed typically increase in precision as they move from the top to the bottom in the graph
and from left to right, i.e. from a total cost approach to a measured mile approach.  This also reflects the
order of preference in the research literature26.

The cost, effort, and expertise required for quantifying the loss normally increases from left to right.
Horizontally the availability and quality of contemporaneous documentation required increases as the
more detailed methods are used.

Before embarking on a productivity loss analysis, the claimant should carefully consider whether the loss
can be recast as an impact of specifically definable extra work.  If that is the case, then that productivity
loss should be incorporated into the estimate for the extra work and resolved in that manner.

25
Adapted from Quantified Impacts of Project Change, Ibbs, Long, Nguyen and Lee, Journal of Professional Issues in Engineering
Education and Practice 2007.
26
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Tribunals appear to be more favourably impressed by damage calculations related directly to the project
in dispute and supported by contemporaneous project documentation.27 Therefore, recommended
practice for preparing a lost productivity calculation is to utilise, if possible, one of the techniques listed
in the category of Project Practice Based Methods set out below.

These methodologies are project specific and supported by people and records directly involved at the
time of the dispute or the disputed work. That direct relationship to the work and the events in
question are what gives the approach its appeal to a tribunal in favour of a more theoretical or
generalist approach.

If there is insufficient information available from contemporaneous project documentation to support
one of these techniques, recommended practice then is to use one of the methods listed under the
category Project Comparison Studies. These methodologies, too, are project specific but rely upon
different forms of contemporaneous documentation.

Unfortunately appropriate contemporaneous project documentation is not always available.  Estimated
costs are, of course, recognised as a legitimate way to calculate damages once entitlement and
causation are sufficiently proven. Legal systems generally recognise that damages cannot always be
calculated with mathematical certainty. Further, it is recognised that contractors frequently have to
prepare and live with cost estimates. Therefore, in the absence of other proof of damages, the legal
system may allow estimates to establish damages.28

Estimated damages may be acceptable, under appropriate circumstances, but are more subject to
challenge than direct project costs. Of the damage calculation and estimating methods available,
recommended practice is to use first, one of the studies listed in the Specialty Industry Studies
category. These are specialty studies of specific types of problems and are, generally, based on a
number of actual construction projects.  Of course, to utilise one of these studies, the causation of the
lost productivity should be appropriate for the particular problem studied.

If none of the specialised studies are applicable to the situation in question recommended practice is to
utilise one of the studies listed in the General Industry Studies categories.

These studies are subject to greater challenge because they are industry wide and not subject or project
specific.  In addition, the basic data is sometimes derived from a non‐construction environment.  Finally,
these studies were largely intended as “forward pricing guides”, as such, their intended purpose was
distinctly different.

Notwithstanding these criticisms, in the absence of more reliable techniques, claimants have been
allowed to use these studies once entitlement and causation have been sufficiently proven.

If the contractor preparing a lost productivity damages calculation can demonstrate entitlement and
causation but is unable to utilise one of the techniques previously noted, recommended practice is then
to use one of the methods listed in the Cost Basis category.

To successfully utilise one of these techniques, the claimant generally has to overcome some difficult
legal hurdles, discussed in more detail below. But, if these challenges can be met, then these techniques
may be allowed as a measure of lost productivity.

27
For a more thorough discussion of this point see Schwartzkopf, William and John J. McNamara, Calculating Construction
Damages, 2nd Edition, Aspen Law & Business, New York, 2001, §1.03. See also, Wickwire, Jon M., Thomas J. Driscoll, Stephen B.
Hurlbutt and Scott B. Hillman, Construction Scheduling: Preparation, Liability and Claims, 2nd Edition, Aspen Law & Business,
New York, 2003, §12.04 et. seq. See also, Roy S. Cohen, Survey of Court’s Reactions to Claims for Loss of Productivity and
Inefficiency, Session 612, ABA Public Construction Superconference, December 10, 1998.
28
Schwartzkopf, ibid, §1.03[B].
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Project Practice Based Methods

Measured mile analysis, baseline productivity analysis, system dynamics modelling, earned value
analysis, sampling studies, and comparison studies are all project practice based approaches whose
calculations are drawn from the project records.

As such, they are expected to be more credible than alternative general approaches.  Courts and other
tribunals therefore prefer estimations of damages that are directly linked to the disputed project and
supported by its contemporaneous documentation29. The types of contemporaneous documentation
required are generally different from one method to another. That is, the most suitable method for a
given project can only be determined based upon the available project data.

Measured Mile Analysis

The measured mile approach30 is widely acknowledged as the most acceptable method for calculating
lost productivity costs.

The analysis compares identical tasks in impacted and non‐impacted periods of the project to estimate
the productivity loss caused by the impact of a known series of events31.  It is based on an extrapolation
of actual work hours spent32.  The measured mile calculation might include comparison of similar work
activities and achieve court acceptance33. The attraction of the measured mile is that the actual
contract performance rather than the initial estimate is used for the calculations.  As such it compares
actual performance on site with actual performance, not some theoretical planned performance.

29
30
Sometimes referred to as differential studies or measured productivity comparisons.
31
32
Zink, D. A. (1986). “The measured mile: Proving construction inefficiency costs.” Cost Eng., 28(4), 19–21.
33
Jones 2003; Calvey and Zollinger 2003; Association for the Advancement of Cost Engineering (AACE) International, Inc.
(2004). “Estimating lost labor productivity in construction claims.” AACE International Recommended Practice No. 25R‐03.
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The above illustrates a non‐disrupted period of excavation and a later disrupted period where the
volume of excavation per unit of time has been adversely affected by operational and access restrictions
imposed upon the Contractor.

There are several assumptions and prerequisites underlying the measured mile technique:
 First, there must be a non‐impacted or least impacted period, so‐called “measured mile” period,
for the specific type of work being assessed.  The adverse factors affecting productivity during
the measured mile period, if any, must be solely attributable to the contractor;
 Second, the length of this period should be significant compared to the impacted period and the
course of work.  It would be unreasonable to extrapolate 2% of progress into 80% of expected
costs34;
 Third, sufficient amounts of contemporaneous project data should be available for the analysis.
At most the physical units of work completed have to be periodically recorded so that the
cumulative labour hours can be plotted through the course of work.
 Fourth, the project data are assumed to be error free. That is, the contemporaneous
documentation must be accurately recorded by the contractor; and
 Finally, all disruptions during the impacted period are due to one party’s (say, the owner’s)
actions or inactions.  It is extended that other factors unrelated to the claimed impacts have to
be accounted for and removed from the impacted period analysis to the degree these factors
occurred during the measured mile period35.

34
Zink, D. A. (1986). “The measured mile: Proving construction inefficiency costs.” Cost Eng., 28(4), 19–21.
35
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Considerable limitations are embedded in these assumptions. The measured mile analysis becomes
unreliable or even impossible when either a non‐impacted period simply does not exist or that period is
not sizeable. The fact that the analysis requires identical or substantially similar activities for
comparisons can hamper its applicability as the method is inappropriate for unique and complex tasks36.
The reliability of the method is challenged if inaccurate contemporaneous project data is used for the
analysis.  Unfortunately reporting errors are commonplace in projects37.

Other limitations are more implicit.  Projected cumulative labour hours can be extrapolated differently
due to different options of the time frame. Gulezian and Samelian38 pointed out that:
(1) Different time frame and segments selected within the measured mile period may produce
different numbers; and
(2) Variation of daily productivity is concealed to varying extents by the cumulating nature of the
measure mile analysis.

They also argue that the measured mile does not necessarily reflect the productivity normally achieved
by the contractor due to the smoothing effect of successive cumulative data and the nature of variation
in unit productivity values.  In addition, the two average productivity rates, which are readily calculated
and compared for non‐impacted and impacted periods, may mask the fact that a contractor generally
does not attain a single rate of productivity throughout a time period39.

Example Measured Mile Calculation Comparison of Unit Cost for Impacted and Non‐impacted Areas40
The Contractor planned to perform all of the cross taxiway paving on an uninterrupted basis, and to use
paving machines for all of the concrete paving except for the fillet areas, which were to be done by hand
pours.

Because of the engineer's changes in the taxiway lighting and a requirement to put pavement‐sensing
devices in the concrete for a long‐range pavement wear study, the work on the south taxiways was
performed on a sporadic and intermittent basis. In fact, much of it was performed on a hand basis
rather than using the large concrete slip form paving spread.  This caused a substantially greater cost of
performing the work on the south taxiways than could be reasonably anticipated.

The work on the north taxiways was performed under normal conditions, since the changes were all
made prior to the start of work on the north taxiways and the pavement wear study would not be
conducted on the north taxiways. Runway's cost as a result of these changes can be calculated by
comparing the unit cost of labour for the north taxiways (which were essentially non‐impacted) with the
unit cost of labour for the south taxiways (which were substantially impacted). Both the north and
south taxiways were performed during normal paving periods under good weather conditions. The
same labour force and the same equipment (with the exception that the slip form paving spread could
not always be used due to the change) was used on both areas.  However, the unit labour cost on the
north taxiways, which were non‐impacted, was approximately half of the cost incurred on the south
taxiways.

36
Loulakis, M. C., and Santiago, S. J. (1999). “Getting the most out of your ‘measured mile’ approach.” Civ. Eng. (N.Y.), 69(11),
69.
37
Thomas, H. R., and Sanvido, V. E. (2000). “Quantification of losses caused by labor inefficiencies: Where is the elusive
measured mile?” Constr. Law Bus., 1.
38
Gulezian, R., and Samelian, F. (2003). “Baseline determination in construction labor productivity‐loss claims.” J. Manage. Eng.,
19(4), 160–165.
39
Finke, M. R. (1998). “Statistical evaluations of measured mile productivity claims.” Cost Eng., 40(12), 28–30.
40
Drawn from Schwartzkopf, Calculating Lost Labor Productivity in Construction Claims, 2nd Edition.
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On the above information and the following simplistic analysis, the Contractor is entitled to be paid
$549,155 in additional costs that it incurred, as illustrated in the following formula:

Actual North Cross Actual South Cross
Taxiway Production Taxiway Production
Hours 10,116.00 51,969.00
Square Metres Produced 102,256.00 281,746.60
Hours/Square Metre .099 .184

Increase in Unit Labour Rate 0.086

Quantity Affected by Blockout and Light Change 281,746.60
Increased Rate 0.086

Manhour Increase Due to Change 24,096.32
Labour Cost per Manhour $22.79

Total Additional Labour Cost $549,155.17

Baseline Productivity Analysis

This approach was proposed in order to avoid some of the limitations and impractical assumptions of a
current measured mile analysis.  Similar to the measured mile method, baseline analysis relies on the
contractor’s actual performance of the project being analysed. A central point of this analysis is to
establish the baseline productivity. It represents the best and most consistent productivity the
contractor was able to achieve on the project41. Analysing a 42 project database42 revealed that the
baseline productivity mainly depends on the complexity of the design and the work methods used.
Unlike the measured mile analysis, a baseline analysis neither needs defined non‐impacted and
impacted periods nor be consecutive reporting periods in the baseline time frame43.  In other words, the
baseline analysis can be more flexible and hence more applicable in current practice44.

However, the process has not obtained consensus among studies though it is generally agreed that
using individual productivity values is better than cumulative productivity for the calculations.  This may
be due to varying views on the baseline productivity. Unlike Thomas and Završki45, Gulezian and
Samelian46 noted that the baseline productivity reflects the normal operating performance of a
contractor.

41
Thomas, H. R., and Završki, I. (1999). “Construction baseline productivity: Theory and practice.” J. Constr. Eng. Manage.,
125(5), 295–303.
42
125(5), 295–303.
43
125(5), 295–303
44
A determining process of the baseline productivity can be found in Thomas and Završki (1999), Thomas and Sanvido (2000),
and Gulezian, R., and Samelian, F. (2003). “Baseline determination in construction labor productivity‐loss claims.” J. Manage.
Eng., 19(4), 160–165.
45
125(5), 295–303.
46
19(4), 160–165.
Page | 16


Thomas and Završki47 and Thomas and Sanvido48 determine the baseline productivity as “the median of
the individual productivity values in the baseline subset.”  Gulezian and Samelian49 calculate it as “the
mean productivity of the points falling within the control limits” after applying an iterative process of an
individuals’ control chart to deal with different sources of variation of periodically reported productivity
values.

Although the baseline analysis solves several problems associated with the measured mile approach, it
is still limited. The way of calculating the baseline productivity should be more scientific and
straightforward, subject to properly dealing with the reliability of reported data, variation of
productivity values, and casual linkages to disruptions and inefficiency.  Some shortcomings are related
to the establishment of the baseline sample as in Thomas and Završki50 and Thomas and Sanvido51. They
are:
(1) The baseline sample is identified according to the best daily output instead of the best daily
productivity; and
(2) The 10% requirement for the baseline sample size is arbitrary and not based upon scientific
principles52.

In addition it is agreed that the baseline analysis is a cause and effect analysis, yet it is qualitative or very
roughly approximate in nature as in Thomas53. There has been no sound method for which damages
induced by the owner and contractor are classified and quantified during a disputed period.  Especially,
multiple and/or simultaneous owner and contractor‐caused disruptions are not uncommon in real life.

System Dynamics Modelling

System dynamics (‘SD’) modelling has been employed to understand the behaviour of various natural,
social, and engineered systems54. Developed at MIT55 in the late 1950’s, SD is widely used in the
defence industry.

A number of delay and disruption claims have been successfully settled with extensive support of SD
modelling.  One such successful story was the development and application of a SD computer simulation
model to resolve a $500 million shipbuilder claim consisting of the direct impact and the “ripple effects”
between Ingalls Shipbuilding and the U.S. Navy in the 1970s56. Other successful applications of SD
modelling in delay and disruption claims and lawsuits have also been reported57.

47
125(5), 295–303.
48
49
19(4), 160–165.
50
125(5), 295–303.
51
52
Ibbs, W., and Liu, M. (2005). “Improved measured mile analysis technique.” J. Constr. Eng. Manage., 131(12), 1249–1256.
53
Thomas, H. R. (2005). “Causation and cause‐effect analyses.” Construction claims online, WPL, 3(4).
54
Its principles, concepts, and tools can be found in Forrester, J. (1961). Industrial dynamics, Pegasus Communications,
Waltham, Mass, Richardson, G., and Pugh, A. (1981). Introduction to system dynamics modeling with dynamo, Pegasus
Communications, Waltham, Mass, and Sterman, J. D. (2000). Business dynamics, system thinking, and modelling for a complex
world, Irwin McGraw‐Hill, New York.
55
Massachusetts Institute of Technology.
56
Cooper, K. G. (1980). “Naval ship production: A claim settled and a framework built.” Interfaces, 10(6), 20–36.
57
Ackermann, F., Eden, C., and Williams, T. (1997). “Modeling for litigation: Mixing qualitative and quantitative approaches.”
Interfaces, 27, 48–65; Eden, C., Williams, T., Ackermann, F., and Howick, S.(2000). “On the nature of disruption and delay.” J.
Oper. Res. Soc. Jpn., 51, 291–300; Williams, T. M., Ackermann, F., and Eden, C. (2003). “Structuring a disruption and delay
claim.” Eur. J. Oper. Res., 148, 192–204.
Page | 17


The SD approach seeks to create a computer model of the project that maps all relationships and
feedback loops in a comprehensive dynamic model. A simplistic representation of that model may look
something like:

The sequence of modelled events may run along the following lines:

Page | 18


Page | 19


Page | 20


Problems early in the project propagate to downstream work.  Change impacts originally isolated in the
engineering phase may end up affecting construction as well.  There another similar set of dynamics is
triggered, with the addition of some physical impacts as well, such as crowding (congestion, ‘trade‐
stacking’).   All these dynamic effects in construction, as they affect labour productivity, can amplify the
magnitude of disruption impacts from changes.

Illustrations drawn from Project Changes: Sources, Impacts, Mitigation, Pricing, Litigation & Excellence, PA Consulting Group

By using SD modelling quantification of cumulative impacts can overcome one of the limitations of the
measured mile and baseline analyses. As noted earlier the two methods are not able to easily
accommodate multiple and/or concurrent disruptions caused by different project parties. SD models
can quantify owner‐responsible delay and disruption impact costs and demonstrate the cause and effect
relationship of the cumulative impacts58.  A key feature of SD simulation modelling is that it allows and
directs answering a pool of “what if” questions such as: What if one particular category of disruptions
had not occurred but all others had?  What if the owner interventions had not occurred?59.  In addition,
it visualises causality and allows for validation of causal logic in quantitative terms and against actual
data at any period of the project in dispute60.

SD modelling has not achieved popularity in construction disputes compared to the measured mile
analysis.

58
Cooper, K. G. (1980). “Naval ship production: A claim settled and a framework built.” Interfaces, 10(6), 20–36.
59
Cooper, K. G. (1980). “Naval ship production: A claim settled and a framework built.” Interfaces, 10(6), 20–3; Eden, C.,
Williams, T., and Ackermann, F. (2005). “Analysing project cost overruns: Comparing the ‘measured mile’ analysis and system
dynamics modelling.” Int. J. Proj. Manage., 23, 135–139.
60
Eden, C., Williams, T., and Ackermann, F. (2005). “Analysing project cost overruns: Comparing the ‘measured mile’ analysis
and system dynamics modelling.” Int. J. Proj. Manage., 23, 135–139.
Page | 21


One main reason is that SD simulation models are not readily understood due to the dynamic
complexity and quantitative nature of those models61. In addition, unless the SD model is properly
validated, it is pointless, barely credible, and therefore useless.

Validation of a SD model is problematic and time consuming and requires extensive expertise of the SD
methodology.  In some circumstances, it is assumed that the reasonableness of the original estimate in
SD modelling can draw inaccurate and unpersuasive quantum of damages. Also, although the causal
coefficients indicating the relationships between activities are very important to the accuracy of a SD
model, they are not easy to estimate62.

Earned Value Analysis

Productivity measurement is sometimes difficult when there is insufficient information concerning the
physical units of work installed on the project. In these situations, a simplistic form63 of the earned
value analysis method can be utilised to calculate estimated labour hours.64  The contractor’s estimate
or alternatively the monetary value of payment applications, contract amounts or unit prices can be
used to determine labour hours, when they were expended and, possibly, on what activities.65  Physical
units of work completed multiplied by budget unit rates can be used to determine earned hours.  The
earned hours are then compared to the actual hours expended for the period of the impact and the
difference between the two may be used to calculate the productivity loss experienced.

Earned value measurement of contemporaneous project documentation, such as percentages complete
from schedule updates or payment applications can assist with calculating labour productivity.66
Additionally, the claimant may calculate the actual revenue per hour of labour versus the planned
revenue per hour, as an alternative.67  Earned value analysis may also be utilised to calculate estimated
labour hours.68

When using the earned value analysis technique, it is cautioned that the budget used to generate the
earned value metrics be carefully reviewed and verified for reasonableness.  Any earned value analysis
based upon an unreasonable budget is highly suspect. Finally, it is noted that a fully resource loaded
(labour and quantities) CPM schedule is a good source for obtaining earned value metrics and allows for
like‐time causation analysis.

An earned value analysis can also be used to estimate the cumulative impacts, especially when the
physical units of work completed have not been recorded adequately for employing a more reliable
method like the measured mile and baseline analyses.

61
Howick, S. (2005). “Using system dynamics models with litigation audiences.” Eur. J. Oper. Res., 162, 239–250.
62
Ibbs, W., and Liu, M. (2005). “System dynamic modeling of delay and disruption claims.” Cost Eng., 47(6), 12–15.
63
The use of the term “earned value” means different things to different people. In this context, “simplified earned value” is
used to distinguish between form Earned Value as required by the US Government on many of their projects and earned value
as practiced by many EPC contractors. See for example Kenneth K. Humphreys, Jelen’s Cost and Optimization Engineering, Third
Edition, McGraw Hill, New York, 1991; James M. Neil, Construction Cost Estimating for Project Control, Prentice‐Hall, Inc.,
Englewood Cliffs, New Jersey, 1982; and Skills and Knowledge of Cost Engineering, Fifth Edition, AACE International,
Morgantown, West Virginia, 2004.
64
See Stumpf, George, R., editor, AACEI Professional Practice Guide to Earned Value, AACEI, Morgantown, WV, 1999.
65
See Cass, Donald J., Earned Value Programs for DOE Projects, Cost Engineering, Vol. 42, No. 3, February 2000.
66
See Fleming, Quentin W. and Joel M. Koppelman, Earned Value Project Management, Project Management Institute, Upper
Darby, PA. 1996.
67
See McCally, Bob M., Demonstrated Labor Efficiency: An Effective Cost Control and Analytical Tool, Cost Engineering, Vol. 41,
No. 11, pp. 33 – 37, November 1999.
68
See Jones and Driscoll, Ibid, page B‐24.
Page | 22


For a project, the difference between earned hours determined from the earned value analysis method
and actual hours expended for an impacted period can be used to compute the inefficiency suffered69.
As an earned value analysis is based on the percent complete and the budget, the credibility of the
method can be questionable.  The reasons are that:
(1) The percent complete method is not as detailed and accurate as the physical units of work
completed method70 used in the previous quantifying methods; and
(2) The original estimate is likely to be unsubstantiated. Any earned value analysis relying on an
unreasonable budget is very doubtful71.

Sampling Methods

Two sampling methods used for estimating lost productivity are work sampling and craftsmen
questionnaire sampling methods.  Introduction to these methods can be found elsewhere72.

Work sampling is a method in which a large number of direct observations of tradesmen are made to
determine what they are doing at various points in time. Work sampling is defined as “An application of
random sampling techniques to the study of work activities so that the proportions of time devoted to
different elements of work can be estimated with a given degree of statistical validity.”73

From these observations the claimant determines, on a percentage basis, how much time is spent
between direct work (pay item work); support work (moving tools and materials to the work location);
or delays (time when no work is being performed).  By performing a number of work sampling studies,
the analyst can draw comparisons of productivity before and after known events, between work
activities or crews, etc.  Work sampling has been offered as a means of determining productivity loss but
it can only be performed during the life of the project and is not compatible with a hindsight analysis
effort.74

The sampling methods are typically simple and inexpensive to analyse labour productivity. Although
they can be used for lost productivity claims, their trustworthiness is not high as they are only a sampled
measure of labour productivity.

For instance, an assumption of work sampling that there is a positive relationship between productive
time and labour productivity was found to be false75.

The questionnaire approach allows craftsmen to estimate the amount of lost productive time in the field
on a daily or weekly basis, identifying the reason for the lost time. While, perhaps, not the most
scientific of studies, this is contemporaneous documentation if administered properly.  The claimant can
then tie the results of such a survey to the entitlement and causation arguments.76

69
70
71
72
e.g., Oglesby, C. H., Parker, H. W., and Howell, G. A. (1989). Productivity improvement in construction, McGraw‐Hill, New
York..
73
American Institute of Industrial Engineers, American National Standard Z‐94.11, Industrial Engineering Terminology 11‐20
(1989).
74
See Fwu‐Shiun Liou and John D. Borcherding, Work Sampling Can Predict Unit Rate Productivity, Journal of Construction
Engineering and Management, Vol. 112, No. 1, page 90 (March, 1986). See also, Jenkins, James L. and Daryl L. Orth, Productivity
Improvement Through Work Sampling, Cost Engineering, Vol. 46, No. 3, pp. 27 – 32, (March 2004).
75
Thomas, H. R. (1991). “Labor productivity and work sampling: The bottom line.” J. Constr. Eng. Manage., 117(3), 423–444..
76
Luh‐Mann Chang and John D. Borcherding, Evaluation of Craftsmen Questionnaires, Journal of Construction Engineering and
Management, Volume 111, No. 4, page 426. (December, 1985)
Page | 23


A variation of this method is the use of a Craftsmen Questionnaire at the end of the job, to confirm or
modify a productivity loss analysis performed utilising another method. For example, a Board of
Contract Appeals case allowed a Craftsmen Questionnaire to be used as a modifier of an industry‐wide
study and awarded lost productivity costs to a mechanical subcontractor on this basis.77

Comparison Studies

Comparison studies can be classified as comparable work and comparable project studies.  AACE78 also
classifies the comparable work studies in two forms:
(1) The contractor estimates lost productivity on the impacted period, and then locates an
analogous or similar work activity on the same project, which was non‐impacted and calculates
its productivity; and
(2) The contractor compares productivities during the impacted period and of similar but non‐
impacted work performed by another contractor on the same project.

Comparable project studies are used to contrast the productivities of similar work activities on the
project being analysed and a similar project.

The successful use of comparison studies can be difficult to secure given that the definition of similar
work or a similar project are rarely agreed by project parties.  As such baseline productivity analysis or
system dynamics modelling should be considered for sizable claims when there is no clear non‐impacted
period. The other methods can be adopted as complementary and used to further substantiate the
outcome results achieved.  There may be times when they are the best alternative available.

Industry‐Based Methods

Specialty industry and general industry studies are called the industry based methods.  As their names
imply a specialty, industry study employs results of specific studies directly related to the cause of
damages, whereas a general industry study is based on industry‐wide manuals and/or reports. The
specific studies can be about acceleration, learning curve, overtime, weather, and so forth79. The
industry based analyses may be employed when there is insufficient project documentation.  They can
also be used with another method to augment supportive evidence of damages.  In general, although
the industry based methods are quick and inexpensive, their use in calculating lost productivity is not
the first preference.

Cost‐Based Methods

If it is possible to demonstrate entitlement and causation but there is insufficient project documentation
to support damage calculations using any of the above techniques, recommended practice is to use one
of the costing methods set forth below.  These methods require analysis of the project job cost records.
The purpose of such preliminary analysis is to determine actual direct labour hours and costs (having

77
See Hensel Phelps Construction Co., GSBCA Nos. 14,744 & 14,877, 01‐1 BCA ¶ 31,249. January 11, 2001.
78
79
Sources of these qualitative and/or quantitative studies for various subjects can be found in Borcherding, J. D., and Alarcon, L.
F. (1991). “Quantitative effects on productivity.” Constr. Lawyer, 11(1) and Association for the Advancement of Cost
Engineering (AACE) International, Inc. (2004). “Estimating lost labor productivity in construction claims.” AACE International
Recommended Practice No. 25R‐03.
Page | 24


stripped out materials, installed equipment, supplies, field and home office overhead, small tools and
consumables, etc.).

Total cost and modified total cost methods are grouped into cost based methods. AACE80 further
divides a total cost method into a total unit cost and a total labour cost method.  Under the total cost
method, the contractor subtracts its estimated labour costs from the costs actually incurred to arrive at
the resulting overrun as the basis for its inefficiency claims81.  The major difference between the total
cost and modified total cost methods is that damages quantified by modified total cost calculation takes
into account unreasonable estimates and/or inefficiencies due to contractor’s problems. Thus, the
second method, out of the two, is preferable.

Successful use of the cost based methods is limited. In order to employ a total cost analysis, a
contractor generally has to prove the following requirements:
(1) The impracticability of proving actual losses directly;
(2) The reasonableness of its bid;
(3) The reasonableness of its actual costs; and
(4) Lack of responsibility for the added costs82.

The requirements for the use of the modified total cost method are similar but the bid and actual costs
should be reasonable after adjustment

Other Quantifying Methods

There are other inefficiency estimations such as expert testimony and jury verdict. A considerable
portion of lost productivity calculations is based primarily upon an expert’s testimony83.  Although this
method might work, it is extremely uncertain due to a lack of supporting analysis. Similarly, the jury
verdict approach that is occasionally applied by USA boards, courts, and other bodies to determine
damages has no ground on which a contractor should rely.

80
81
Jones, R. M. (2003). “Update on proving and pricing inefficiency claims.” Constr. Lawyer, Summer, 3–11; Klanac, G. P., and
Nelson, E. L. (2004). “Trends in construction lost productivity claims.” J. Profl. Issues Eng. Educ. Pract., 130(3), 226–236.
82
Centex Bateson Construction Co., VABCA No. 4613, 99‐1 BCA ¶30,153 at 149,261, 1998.
83
Sanders, M. C., and Nagata, M. F. (2003). “Assessing methodologies for quantifying lost productivity.” AACE Int. Transactions,
CDR.18, 1–8.
Page | 25


Matching the Quantifying Methods with Project Practice

The above figure84 presents a framework from which the suitability of available approaches for analysis
and quantifying the effects of disruption may be discerned.  This selection process is primarily based on
the availability and the characteristics of information available set against the degree of reliability of the
quantifying method. Available information can be from particular project practice and/or industry
studies.

A series of questions are asked to select the appropriate quantifying method.  Accordingly, the matching
process structures critical questions by various decision points.  These decision points are organised in
such a way that more general questions regarding project practice arise first so that available methods
can gradually be classified in terms of their feasibility.  Finally, the most advantageous method emerges
among the feasible set for a certain type of project data and industry studies.  The relative advantages
and disadvantages of the lost productivity quantifying methods are discussed in the previous section.

84
Adapted from Quantified Impacts of Project Change, Ibbs, Long, Nguyen and Lee, Journal of Professional Issues in Engineering
Education and Practice 2007.
Page | 26


The above framework recommends the most favoured approach rather than a set of possible ones.  This
means that, for example, an earned value analysis can also be used in case a measured mile study is not
available. However, the measured mile method is most favoured in that circumstance and hence is
recommended. In addition, comparison studies do not appear in the possible outcomes of the
framework since much more credible methods such as baseline productivity analysis and system
dynamics modelling are preferred when time, available documents, and resources permit.

Conclusions

Under appropriate circumstances, all of the methods set forth herein are technically acceptable.  Of all
the methods identified above, the most reliable are those reliant upon the analysis of factual,
contemporaneous information drawn from the specific project in question, i.e. Project Specific Studies.

These methods are based upon contemporaneous documentation and knowledge from the project.
Thus, they are the closest to approximating actual damages from the project.  All other methodologies
discussed are estimating techniques with varying degrees of reliability. Therefore, they must be
considered less robust.  This again highlights the importance of keeping good records from the outset of
the project.

To reliably quantify and successfully claim for lost productivity, damages have to be associated with
cause.  Resultant injury goes hand‐in‐hand with liability and causation to form the “triad of proof.”

Page | 27


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Variations, Time Limits and Unanticipated Consequences, Ronan Champion, Society of Construction Law, May 2007

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