TIOBEs index is fundamentally flawed, I've posted here analysing why on numerous occasions and in great detail, and whilst my posts on the topic have always been modded to +5 Slashdot still regularly posts drivel based upon it, and people still seem to debate those stories even though they have exactly no merit whatsoever due to the fact the data behind the story is fundamentally broken.
I still have literally no idea why Slashdot posts stories based on TIOBE, and why anyone bothers to debate those stories as if the premise they're dragging from the index has any merit whatsoever. I can only assume TIOBE pays Slashdot for Slashvertisments at this point.
I'll give TIOBE credit, it has in the last year or so updated it's methodology to be slightly less than worthless rather than just completely worthless, but it's still ultimately just a shade of worthless in it's methodology. It looks like they're now using someone who passed high school statistics, rather than someone that failed it. They really need at absolute minimum a statistics graduate though if their index is to be of any value.
I've long said that if they want to drastically increase the value and worth of their index, then rather than counting how many results they get for "C Language" on YouTube, Amazon, Baidu, and Wikipedia which tells us pretty much nothing about it's usage, that they at least switch to using results from Jobsites, and open source project sites. That way they can start to measure what's actually being used, rather than what a bunch of unrelated search engines are confusing their search for.
Consider this, C++ is a (relatively) old language, but one that has been updated, by searching Amazon for "C++ Language" you may therefore get more books on it than any other language, but that tells us absolutely nothing about how much it's being used, as many people who read the early books may have long retired and the books may be entirely irrelevant now, but Amazon still lists them whilst newer C++ developers are buying the newer books it's possible that usage has stayed relatively static for example - the increase in books does not necessarily correlate to an increase in developers. The same problem rings true in other ways for all their other search results.
By using job sites it may still not tell us anything about retirement, but it does at least tell us the trend. Using open source repositorites can be a good indicator of actual usage, though it misses out the entirety of the corporate closed source world which may or may not use a completely different set of technologies.
So whilst TIOBE currently tells us nothing of value, it could be changed to tell us what companies are hiring for and hence using or intending to use, which is helpful, or it could tell us what open source projects are using, which is useful information as it gives you an idea of what open source developers are choosnig to use even if it's not necessarily representative of the whole market.
Short version: TIOBE needs to change it's methology to be meaningful, or Slashdot needs to stop posting stories based on it that are almost certanily incorrect, or at least aren't verifiable by anything from TIOBE.