I hadn't expected the dominance of Java in the "programmers per language"; I should have, but didn't. I also hadn't expected the disparity between Python and Ruby numbers.
I'm looking forward to digging into this further; it's a really useful and interesting dataset!
I think the usefulness is limited by the fact that they haven't explained how they gathered this data. At first glance, the data looks to have some specific quirks (44% Linux users, overwhelmingly in the Finance industry) – you'd have to wonder it that's due to how the survey was conducted.
There are a couple of resources listed in the end. So we've gathered the information from reddit surveys, stackoverflow, our own surveys (with more than 5000 respondents), job ads, various language popularity indexes like Tiobe.
I'm looking forward to digging into this further; it's a really useful and interesting dataset!