  To explore the prevalence of abrupt changes (changepoints) in open source
project activity, we assembled a dataset of 8,919 projects from the World of
Code. Projects were selected based on age, number of commits, and number of
authors. Using the nonparametric PELT algorithm, we identified changepoints in
project activity time series, finding that more than 90% of projects had
between one and six changepoints. Increases and decreases in project activity
occurred with roughly equal frequency. While most changes are relatively small,
on the order of a few authors or few dozen commits per month, there were long
tails of much larger project activity changes. In future work, we plan to focus
on larger changes to search for common open source lifecycle patterns as well
as common responses to external events.
