Methods, systems, and apparatus, including computer programs encoded on computer storage media for automatically determining developer team composition. One of the methods includes obtaining a reference set of snapshots for a code base, each snapshot comprising a representation of source code of the code base at a particular time and being associated with a particular project and a particular developer of a team of developers of the code base; selecting a subset of snapshots; dividing the subset into a plurality of time windows; for each time window and for each developer that committed a snapshot to the reference collection of snapshots during the time window, determining a normalized rating of the developer's skills in each of a plurality of developer activity metrics; and aggregating, for each time window, the normalized ratings for each developer to generate a developer team composition for the fixed period of time.