[cestith]

TIOBE is, AFAICT, using a single web search engine (Google) and searching for a string representing the language like "C programming" or "Ruby programming", and taking a count of results. This favors languages that have a lot written about them due to age, or student interest, or whatever leads people to write a web page about a language.

It'd be interesting, and no more or less valid, to see how many paper books and ebooks have been sold on each.

GitHub takes count of the projects on its own site in each language, but that microcosm may not represent other places. Anecdotally, my employer runs private git repos on private servers, and our ratios don't match GitHub's.

Another interesting metric would be number of job openings. Another would be average pay for a developer mainly using a particular language. Another would be asking people in a scientific poll which languages they use and which ones they enjoy using.