Quantitative Effects of Construction Changes on Labor Productivity

Abstract

This paper details, in quantitative terms, the effects of changes and change orders on labor productivity and efficiency. Data for the analyses were daily productivity values from three industrial projects constructed in the 1989–1992 time frame. A total of 522 workdays of data were collected. None of the data involved disputed work or contract claims. Various analysis techniques were applied to the data, including data sorts and averages, analysis of variance tests, and multiple regression. The results confirm that it is possible to perform changes without negatively impacting labor efficiency. There was no negative effect in fewer than half the days when changes were performed. However, the average effect of all changes was a 30% loss of efficiency. Investigations into the cause of efficiency losses showed that there were disruptions when changes work was performed. A regression analysis showed a 25–50% loss of efficiency depending on the type of disruption. A threefold increase in the number of material availability problems was the most obvious disruption associated with change work.