Revisiting Turnover-Induced Knowledge Loss in Software Projects

In large software projects, tacit knowledge of the system is threatened by developer turnover. When a developer leaves the project, their knowledge may be lost if the other developers do not understand the design decisions made by the leaving developer. Understanding the source code written by leaving developers thus becomes a burden for their successors. In a previous paper, Rigby et al. reported on a case study of turnover-induced knowledge loss in two large projects, Chromium and a project at Avaya, using risk evaluation methods usually applied to financial systems. They found that the two projects were susceptible to large knowledge losses that are more than three times the average loss. We report on a replication of their study on the Chromium project, as well as seven other large and medium-sized open source projects. We also extended theirwork by studying two variations of the knowledge loss metric, as well as the location and persistence of abandoned files. We found that all projects had a similar knowledge loss probability distribution, but extreme knowledge loss can be more severe than those originally discovered in Chromium and the project at Avaya. We also found that, in the systems under study, abandoned files often remained in the system for long periods.