I think 2010 is high because it is when the cvs => git transition happened. In the cvs era, commits are recorded from @fedoraproject.org, and in the git era, by whatever email is in the git commit. So most users are doubled in 2010.
(For email addresses you still have access to, you can add them to a github account, and sign in with github to the site, it will collect those contributions together.)