This is very interesting stuff. What I'd like to know is how you could measure the size of each project. Otherwise this could be easily skewed by a user creating a ton of empty, unfinished, or even dummy projects once they have heard about this study. There isn't really anything stopping them on GitHub.
As a last comment:
The descending grey bands represent the rank quartiles, e.g., the top band is the 100th percentiles, then 80th percentile, etc. If there are 5 of them, doesn't that make them quintiles (which my spellchecker claims isn't a word, haha)?
