TIOBE index
Tiobe programming community index is an ordered list of programming languages, sorted by the frequency of web search using the name of this language as keyword. The index covers searches in Google, Google Blogs, MSN, Yahoo!, Wikipedia and YouTube. The index is updated once a month. The current information is free but the long term statistics over many years of observation is for sale. The index authors think that it may be valuable when accepting various strategic decisions. Tiobe focuses on Turing complete languages, so it does not provide information about the popularity of, for instance, SQL or HTML. Assembly language is also excluded, claiming it is too specific.
According the site, Tiobe index is not about the best programming language or the language in which most lines of code have been written[1]. However the site does claim that the frequency of searches may reflect the number of skilled engineers, courses and jobs worldwide. These claims are criticized in the opposing publications[2].
For many years, Tiobe has been a subject of highly emotional flame wars. In particular, decrease of Perl popularity (while it is in general not ranked very low) raised discussions that maybe this language is "dying" [3], followed by wide negative response from the Perl community [4]. Similarly, the growth of Python (programming language) have been discussed as a success in Python community [5]. Java staying on the top has been interpreted as success [6] but some decline over many years have also raised a discussion if this is as "dying language" [7]. Tiobe index does not give particularly high rank for C#, Fortran and some other notable languages.
Tiobe index is sensitive to the ranking policy of the search engines on that it is based. For instance, in April 2004 Google performed a cleanup action to get rid of unfair attempts to promote the search rank. As a consequence, there was a huge drop for languages such as Java and C++, yet these languages have stayed at the top of the table. To avoid such fluctuations, Tiobe now uses more search engines.