"What proportion of paradox game players, who read and post on the forums,"
I'm saying that this is the selector-- people who read and post on the forums are more likely to have thinking-heavy jobs, or to be university students, because people on the internet are more likely to have thinking jobs or be university students. People who are interested in Paradox's games, which are not exactly the most accessible out there, are more likely to have a thinking job and be interested in economics, history, and run-on sentences. The fanbase is self-selecting, and not because people with lower-paying jobs are any dumber on average AND because it requires certain degrees of imagination
What I disagree with is this half-- "who feel like telling everybody else their age and job."