The Effects of Change on Labor Productivity: Why and How Much

The analysis of productivity data reveals that, on average, labor efficiency is about 70 percent of normal when work is performed on changes; that is, there is a 30 percent loss of labor efficiency that results from the change. (SD-99, p. v)

Additional analyses support the conclusion that changes cause disruptions to the work which negatively affect labor efficiency. The most significant types of disruptions are 1) lack of materials and information and 2) having to perform the work out-of-sequence. These disruptions result in a daily loss of efficiency in the range of 26 to 47 percent. (SD-99, pp. v, 63)

The principal factor leading to disruptions and loss of efficiency is timing of the change. If changes are identified before the work is given to the crafts, the effect of changes on labor productivity is probably minimal. However, if a change is identified by the crew in the field, then productivity is adversely impacted because the crew has to stop work in progress and either wait for information and materials or move to another location and come back later to implement the change. (SD-99, pp. vi, 63)

A conceptual model was described that explained how changes and rework affected labor productivity. The model is based on disruptions. The model states that changes themselves do not cause losses of productivity, but instead cause disruptions to occur. It is these disruptions that cause productivity losses. Changes that can be made that avoid disruptions can be completed with little or no impact on labor. (SD-99, p. 57)

This model is based on the factors that affect labor productivity. The work environment and work to be done are factors that influence the workhours needed to produce the output. This is illustrated in the two figures below. (SD-99, p. 23)

{^widget|(widget_displayname)WatermarkImage|(name)WatermarkImage|(image)%7e%2fCII%2fmedia%2fPublications%2fSD99_Figure9.PNG%3fext%3d.png|(width)|(height)^}