The statistic shown is just that, a statistic, and since I don't have any others, that's all I can show. I know it's just as bad as most other statistics; the other information I have is even more vague than this silly graph.
Fair enough. I was hoping for something more substantial since you were able to quantify your claim, but I guess that was just a case of accidental wording. The part I have a hard time believing is that most existing projects are switching to git. Even if a lot of projects are, there are tons of open source projects. sourceforge alone contains 290808 projects, and they don't provide git repositories (only CVS and svn).
Well, like I said, don't overweight this graph... But since you are starting to pick it apart, we might as well do it properly... What it probably means, is that the number of people installing Debian are increasingly non-developers.
Yup. This is a hypotheses which the graph _does_ give support to at least. :-) Or possibly that there are now more non-developers using popularity contest. (Didn't they change so that it always asks during installation now, instead of you having to enable it manually?)