Somebody should point him towards one of the extensive polls we've had on the subject. Like this example:
http://www.enworld.org/forum/poll.php?pollid=6895&do=showresults
Might be worth adding to his results, though there's probably some overlap of voters.
Interesting to compare the two. The first thing the jumps out (for me, at least) is the high number of votes for Greyhawk relative to the Perkins' poll.
Makes me believe that the EN World perspective would be quite "grognard-skewed" when compared to the total pool of D&D players.