Short of an international software developer cold-call survey, all "language popularity" estimates are going to be weighted towards some specific community.

TIOBE seems weighted towards blog/article writers, using GitHub et al. would be weighted towards the open-source community.. Stack Overflow is also a fairly cohesive community, though a harder one to name: people who ask for help in online Q/A sites?

For instance, I'll bet that none of those three communities overlaps much with government contractors. Within the firms I've worked with, they are very, very hesitant to even use the Internet, let alone participate in it. Information comes from dead trees only. They are also staffed by a much older crowd. And they have a ton of software developers keeping Ada, C, Assembly, and Forth alive and kicking.