Most economists would agree with the importance of productivity
to an individual enterprise, an industry, or an economy. Unfortunately,
no such agreement exists when it comes to an actual, precise
definition of “productivity” and which of the numerous alternative
approaches to measuring productivity are suitable for a given task.
The Concise Oxford Dictionary definitions of “productivity” include:
the power of being productive; efficiency; and the rate at
which goods are produced. Three distinct components of the concept
of productivity are addressed by this definition:
1. Power of being productive is the force behind production
itself;
2. Efficiency is a measure of how well the factors are utilized;
3. Rate is a measure of the output of the factors of production
over a defined period of time.
The term “productivity” is generally used to denote a relationship
between output and the associated inputs used in the production process.
Consequently, construction productivity can be regarded as a
measure of outputs that are obtained by a combination of inputs. In
view of this, Talhouni (1990) and Rakhra (1991) used two measures
of construction productivity: (1) total factor productivity, in which
outputs and all inputs are considered; and (2) partial factor productivity,
often referred to as single factor productivity, in which outputs
and single or selected inputs are considered. Because construction is
a labor-intensive industry, it can be argued that the workforce is the
dominant productive resource; thus, construction productivity is primarily
dependent on human effort and performance (Jarkas 2010).
Thus, labor productivity is a crucial productivity index because of the
concentration of human labor needed to complete a specific task.
Many definitions of CLP exist that reflect the different perspectives
of the construction industry.
Hourly outputs are widely used to measure labor productivity in
construction research (Thomas and Yiakoumis 1987; Sonmez and
Rowings 1998; Hanna et al. 2008), using a labor hour as the input
unit and the physical quantity of the completed work as the output.
For example, concrete placement uses the labor hour as the input
and the cubic yards of concrete as the output. For concrete placement,
labor productivity can be expressed as hours per cubic meter
or cubic meters per hour. The ratio can be in the format of input/
output. As demonstrated in Eq. (1), CLP is measured in actual work
hours per installed quantity; specifically, this pertains to the number
of actual work hours required to perform the appropriate units of
work. When defined in this manner, lower productivity values indicate
better productivity performance. Compared with cost-based
output measures (Eastman and Sacks 2008), measurement by
hourly output avoids many external factors that cause cost variance.
Thus, hourly output is commonly recognized as a reliable measurement
of productivity for construction operational activities:
CLP ¼ Work − hour
Output
¼ Actual work hours
Installed quantity
ð1Þ
One challenge in measuring productivity at the project level is
that the unit of measurement depends on the construction activity.
A concrete placement activity may be measured in cubic meters of
concrete placed per hour, whereas a structural steel placement activity
may be measured in linear meters of steel placed per hour.
Differences exist between production rate levels among job types.
The average production rate for pouring columns is lower than that
for pouring walls because of job characteristics. The American Association
of Cost Engineers (AACE) (2013) defines productivity as
a “relative measure of labor efficiency, either good or bad, when
compared to an established base or norm.” Whereas this relative
nature of productivity creates great difficulties in tracing it as an
absolute value over time, it is possible to gather information
on the movements of the established base, or benchmark, values
(Allmon et al. 2000). Thus, project managers and construction professionals
define labor productivity as a ratio of actual over expected
productivity, expressed mathematically as
Performance ratioðPRÞ
im
¼ Actual productivityim
=Expected productivityim ð2Þ
where i = workday under consideration; and m = activity in project.
An expected productivity was calculated by determining the work
hours and quantities installed on days when no changes or rework,
disruptions, or bad weather were reported. Performance ratio is
a unitless measure that is determined by dividing actual productivity
by baseline productivity; it defines a basis for comparing productivity
data for different job types, eliminating the differences
between production rate levels. A performance ratio (PR) value
greater than unity means that based on the daily quantities, more
work hours were required that day than on the average baseline
day; that is, the productivity was worse than the baseline productivity.
The advantage of this approach is that progress is based on
the installed work, not the work hours consumed, and progress
and performance can be determined regardless of the type of work
performed.
Economists and accountants define labor productivity as the ratio
between total resource input and total product output (Hanna
et al. 2005). The Bureau of Labor Statistics (BLS) in the U.S.
(2006) defines labor productivity as real output per hours worked.
The term “hours” refers to hours actually worked. This measure
excludes vacation, holidays, and sick leave, but includes paid
and unpaid overtime. CLP is adopted as an economic idea at
the industry level and calculated as Eq. (3). Gross product originating
by industry (GPO) is expressed in chained dollars to eliminate
the effect of inflation when comparing data from different time
periods:
CLP ¼ GPO
P12
i¼1 EiHi
ð3Þ
where GPO = gross product originating by the construction
industry in chained dollars; Ei = average number of employees
in month i; and Hi = average number of hours worked in
month i.
There are three approaches for measuring productivity: macroeconomic,
case, and pricing studies (Edkins and Winch 1999). The
major differences between these approaches are the source of data,
the level of aggregation, the boundary/definition of the production
process, and the completeness with which it is described (Chau
andWalker 1988). Depending on the units of input and output, CLP
can be measured in numerous ways (Thomas and Mathews 1986).
It may be measured to identify industry trends and to allow performance
comparisons with other industry sectors (Building Futures
Council 2006). Company-level or project-level CLP measurement
provides internal and external benchmarks for comparison with
company or project norms (Park et al. 2005; Ellis and Lee
2006). For detailed estimating and project scheduling, CLP is measured
by using the input of labor hours and the output of installed
quantities
Most economists would agree with the importance of productivity
to an individual enterprise, an industry, or an economy. Unfortunately,
no such agreement exists when it comes to an actual, precise
definition of “productivity” and which of the numerous alternative
approaches to measuring productivity are suitable for a given task.
The Concise Oxford Dictionary definitions of “productivity” include:
the power of being productive; efficiency; and the rate at
which goods are produced. Three distinct components of the concept
of productivity are addressed by this definition:
1. Power of being productive is the force behind production
itself;
2. Efficiency is a measure of how well the factors are utilized;
3. Rate is a measure of the output of the factors of production
over a defined period of time.
The term “productivity” is generally used to denote a relationship
between output and the associated inputs used in the production process.
Consequently, construction productivity can be regarded as a
measure of outputs that are obtained by a combination of inputs. In
view of this, Talhouni (1990) and Rakhra (1991) used two measures
of construction productivity: (1) total factor productivity, in which
outputs and all inputs are considered; and (2) partial factor productivity,
often referred to as single factor productivity, in which outputs
and single or selected inputs are considered. Because construction is
a labor-intensive industry, it can be argued that the workforce is the
dominant productive resource; thus, construction productivity is primarily
dependent on human effort and performance (Jarkas 2010).
Thus, labor productivity is a crucial productivity index because of the
concentration of human labor needed to complete a specific task.
Many definitions of CLP exist that reflect the different perspectives
of the construction industry.
Hourly outputs are widely used to measure labor productivity in
construction research (Thomas and Yiakoumis 1987; Sonmez and
Rowings 1998; Hanna et al. 2008), using a labor hour as the input
unit and the physical quantity of the completed work as the output.
For example, concrete placement uses the labor hour as the input
and the cubic yards of concrete as the output. For concrete placement,
labor productivity can be expressed as hours per cubic meter
or cubic meters per hour. The ratio can be in the format of input/
output. As demonstrated in Eq. (1), CLP is measured in actual work
hours per installed quantity; specifically, this pertains to the number
of actual work hours required to perform the appropriate units of
work. When defined in this manner, lower productivity values indicate
better productivity performance. Compared with cost-based
output measures (Eastman and Sacks 2008), measurement by
hourly output avoids many external factors that cause cost variance.
Thus, hourly output is commonly recognized as a reliable measurement
of productivity for construction operational activities:
CLP ¼ Work − hour
Output
¼ Actual work hours
Installed quantity
ð1Þ
One challenge in measuring productivity at the project level is
that the unit of measurement depends on the construction activity.
A concrete placement activity may be measured in cubic meters of
concrete placed per hour, whereas a structural steel placement activity
may be measured in linear meters of steel placed per hour.
Differences exist between production rate levels among job types.
The average production rate for pouring columns is lower than that
for pouring walls because of job characteristics. The American Association
of Cost Engineers (AACE) (2013) defines productivity as
a “relative measure of labor efficiency, either good or bad, when
compared to an established base or norm.” Whereas this relative
nature of productivity creates great difficulties in tracing it as an
absolute value over time, it is possible to gather information
on the movements of the established base, or benchmark, values
(Allmon et al. 2000). Thus, project managers and construction professionals
define labor productivity as a ratio of actual over expected
productivity, expressed mathematically as
Performance ratioðPRÞ
im
¼ Actual productivityim
=Expected productivityim ð2Þ
where i = workday under consideration; and m = activity in project.
An expected productivity was calculated by determining the work
hours and quantities installed on days when no changes or rework,
disruptions, or bad weather were reported. Performance ratio is
a unitless measure that is determined by dividing actual productivity
by baseline productivity; it defines a basis for comparing productivity
data for different job types, eliminating the differences
between production rate levels. A performance ratio (PR) value
greater than unity means that based on the daily quantities, more
work hours were required that day than on the average baseline
day; that is, the productivity was worse than the baseline productivity.
The advantage of this approach is that progress is based on
the installed work, not the work hours consumed, and progress
and performance can be determined regardless of the type of work
performed.
Economists and accountants define labor productivity as the ratio
between total resource input and total product output (Hanna
et al. 2005). The Bureau of Labor Statistics (BLS) in the U.S.
(2006) defines labor productivity as real output per hours worked.
The term “hours” refers to hours actually worked. This measure
excludes vacation, holidays, and sick leave, but includes paid
and unpaid overtime. CLP is adopted as an economic idea at
the industry level and calculated as Eq. (3). Gross product originating
by industry (GPO) is expressed in chained dollars to eliminate
the effect of inflation when comparing data from different time
periods:
CLP ¼ GPO
P12
i¼1 EiHi
ð3Þ
where GPO = gross product originating by the construction
industry in chained dollars; Ei = average number of employees
in month i; and Hi = average number of hours worked in
month i.
There are three approaches for measuring productivity: macroeconomic,
case, and pricing studies (Edkins and Winch 1999). The
major differences between these approaches are the source of data,
the level of aggregation, the boundary/definition of the production
process, and the completeness with which it is described (Chau
andWalker 1988). Depending on the units of input and output, CLP
can be measured in numerous ways (Thomas and Mathews 1986).
It may be measured to identify industry trends and to allow performance
comparisons with other industry sectors (Building Futures
Council 2006). Company-level or project-level CLP measurement
provides internal and external benchmarks for comparison with
company or project norms (Park et al. 2005; Ellis and Lee
2006). For detailed estimating and project scheduling, CLP is measured
by using the input of labor hours and the output of installed
quantities
การแปล กรุณารอสักครู่..
