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?