You have to remind yourself to take this kind of figure with a grain of salt, since every measurement technique has some kind of bias. The StackOverflow survey

You have to remind yourself to take this kind of figure with a grain of salt, since every measurement technique has some kind of bias. The StackOverflow survey specifically targets SO users, Google Trends might overestimate languages that receive lots of queries due to less experienced programmers or poor documentation, and it is truly impossible to scan the entire web to find which CMS powers each site (especially since customized CMS installations might not have telltale signs that others do).