[zmmmmm]

The big problem is all the major indexes are driven by search engine measures, and those themselves are highly sensitive to any change in the underlying search engine methodology itself. So a small change in Google's ranking algorithm will see a language move up or down dozens of places.

I would tend to focus more on job ads personally because those are at least linked to "real intent" to use a language for something tangible. You don't put it in an ad because something is controversial or had a lot of news lately etc. which can all lead to things being Googled a lot or getting a spurt of search activity.

Github's index is nice in that it is based on actual code, but then it's also heavily biased by what is open source and therefore doesn't fully reflect industry use of languages (which is why I think it deviates from other indexes to put Javascript and Python a bit higher, and less emphasis on say Java and C#).