> The ratings are based on the number of skilled engineers world-wide, courses and third party vendors. Popular search engines such as Google, Bing, Yahoo!, Wikipedia, Amazon, YouTube and Baidu are used to calculate the ratings.

I'm not sure what that means, but I'm skeptical. Java for example shows a steady decline over the whole span of the graph. Then in 2015 it has a massive surge, then in 2016 a massive decline. C shows a similarly enormous decline , of over 50% in 2016. Did the amount of C programmers really drop by half in 2016?

Also, JavaScript is at only 2x it's 2004 figure on the graph.

That really does stand out. There simply has to be something wrong with their JS numbers.

IMO, this list has very low correlation with what programmers spend their time on. Yes, they write

"The ratings are based on the number of skilled engineers world-wide, courses and third party vendors".

but effectively count search engine hits on "+foo language" (https://tiobe.com/tiobe-index/programming-languages-definiti...) on quite a few sites, over half of them Google properties, so they probably double-count a lot, and including IMO weird choices such as eBay.com.

So, even disregarding the question whether that can lead to ratings "based on the number of skilled engineers world-wide, courses and third party vendors" any tweak Google makes to their search algorithm hugely affects their results.