Here are some charts that are drawn in the style of the US movie box office charts, but for different data.
I found it interesting to see that while CMUCL development is currently dominated by a only few people, it's not much different than it's ever been.
It's also interesting to see how different SBCL contributors have waxed and waned in activity, and how many active contributors it's seen over time after wnewman's initial big push.
CMUCL has a much longer overall CVS history, with info dating back to 1990. You can see the full CMUCL-only chart here.
The data was gathered by using cvs log | grep ^date.
If you have any questions or comments, please let me know.