Popularity of CAS programming languages: Maxima, Maple, Mathematica

A few months ago, inspired by the PYPL PopularitY of Programming Language,  I compared Google trends data for the 3M of CAS software:  Maxima, Maple, and Mathematica based searches of the form “<language> tutorial”.  The result was that Maxima seems to be slowly increasing in popularity  with about 20% of the interest in the 3M.

Today I saw another popularity metric: The TIOBE index.  Using their methodology of Google trends data for the search string <language> + programming, I have these  results for the proportion of searches among the 3M:



Popularity of CAS software: Maxima, Mathematica, Maple

I was looking recently at the PYPL PopularitY of Programming Language.

That site ranks popularity of programming languages (Java is #1)  using Google Trends tools based on searches of the form <Language Name> Tutorial.  I did my own Google Trend search, comparing the 3M of Computer Algebra Systems:  Maple, Mathematica, and Maxima using the Tutorial criteria as at PYPL.

With the data from Google Trends, I computed the proportion of the total 3M monthly searches for each program.  Here’s how that looks over time since 2004:


It appears to me that Maxima is slowly and steadily gaining with nearly 20% share, Maple is currently at about 30%, and Mathematica at 50%.  Does anybody know what happened between 2006 and 2013 to account for the increase in popularity of Mathematica and decrease for Maple?