Dangers in using earned duration and other earned value metrics to measure a project’s schedule performance

Earned value metrics are well known measures for assessing the schedule performance of projects. In response to deficiencies from using activity costs in traditional earned value metrics for evaluating a project’s schedule performance, earned duration management was proposed as an alternative measurement approach. In particular, earned duration management gives a new measure of a project’s schedule performance, called the Duration Performance Index, which purports to show how well the project is doing in achieving its target completion date. Herein, this paper demonstrates that, because of the confounding impact of parallel activities in a project, the Duration Performance Index can yield false positives and false negatives about a project’s schedule status. And it shows that claims made about the Index are at best guaranteed to be true for an arbitrarily small window of time. The paper concludes with the observation that earned value metrics for assessing a project’s schedule performance all suffer from the same confounding impact of parallel activities, as well as other issues; and that research on other approaches is needed.