[fabian2k]

I'm not convinced that SE activity measures difficulty. But it certainly is affected by much more than just popularity. I could imagine it measuring the total API surface, as you can ask more questions about larger subjects.

It's certainly a deeply flawed measure, but then pure search engine hits like TIOBE are likely much worse.

[weberc2]

To be clear, I don't think it measures difficulty, but difficulty is necessarily a driver of the metric. A complex language is going to generate more questions than a small, intuitive language.

[marcosdumay]

Specifically, complexity will generate more questions than difficulty.

[weberc2]

No, it can’t by definition. Complexity is a type of difficulty. :)