openhub.net has a comparion of the number of public repositories on the net, based on searching public hosting services on the net. Git just passed Subversion after the number of Git repositories has exploded lately. It seems as lots of new repositories were created after cpython changed to Git in February.
I've been tracking the development on <https://www.openhub.net/repositories/compare> since 2014-08, and all the data since then are availble on
https://gitlab.com/sunny256/openhub-repositories and https://github.com/sunny256/openhub-repositories
Current status:
https://gitlab.com/sunny256/openhub-repositories/blob/master/status.txt
SVG graphs are available on
https://gitlab.com/sunny256/openhub-repositories/tree/master/graph
Regards, Øyvind
+-| Øyvind A. Holm <sunny@sunbase.org> - N 60.37604° E 5.33339° |-+ | OpenPGP: 0xFB0CBEE894A506E5 - http://www.sunbase.org/pubkey.asc | | Fingerprint: A006 05D6 E676 B319 55E2 E77E FB0C BEE8 94A5 06E5 | +------------| 27e0042e-3985-11e7-b3fc-db5caa6d21d3 |-------------+