>>All-in-all I'd rate this as just another piece of useless web-published "information".
>
>That may be so - but then, the question arises: where to get more or less trustworthy information on what languages are the most used / most in demand?

I have no idea, but it sure looks to me that this isn't it!

What does "world-wide availability of skilled engineers, courses and third party vendors." have to do with the actual "popularity" of a language?
I have no idea how they 'measure' "world-wide availability of skilled engineers" but it could be that a high availability represents a language in decline. And how do they verify this stuff? I've seen people put Xxxxx on their resume because they worked in a shop where Xxxxx was in use but they didn't use it themselves!
What does "world-wide availability of courses" tell anyone? Are they assuming that these courses are actually offerred AND attended? Again, who verifies this? It would be much more interesting if they had the number of 'graduates' for those courses! I bet many course offerers have some courses in their curriculum just to get an enquiry, then press the inquirer to choose something else instead. A common business practise elsewhere, so why not with courses?
Same with "world-wide availability of third party vendors".

Maybe it's impossible to quantify this without a huge investment in time and money.