The new schema conveniently lacks a repository_language field, and is likely the same reason the data in the paper abruptly stops at 2014. (Otherwise, I'd try to reproduce this analysis myself)
For example, I'd expect C# to be more widely used than Go. Maybe the C# people don't share their code on Github, though. Perl should also be more widely used, though maybe that's all on CPAN.
That is not to say it's a perfect language, but I have friends dedicated to python who love using Go and friends who use C and Java that love building personal projects with it. I really had no idea it was gaining adoption in industry and some areas of academia until recently though.
Perhaps there are lots of people/repos/projects that have both python code and C-extensions to python, causing them to cluster together.
There are probably literally millions of Python web apps out there, not to mention sites like Instagram and YouTube running on Python. Python hasn't ever really been a systems language.
Ruby: CSS is 25.76
Python: CSS is 15.75
Go is gaining fastest adoption from C, Ruby and Python developers.
The definition of correlation mentioned in the paper makes zero sense whatsoever and apparently invokes Bayes's rule?
Or are any of them greater than 100?
If this is a good or bad development will (or already is, as we have seen in discussions concerning Go) be the topic of many flame wars.
Python gives Perl and bash a run for the money when it comes to systems scripting, if you're willing to catagorize "systems scripting" as systems programming.
"Java Script" feels like spelling from 1995.