Interesting, but there are other possible conclusions. I don't feel like researching, but among the possibilities that come to mind:
AmWorlds always has a disproportionate local representation.
Variations between average ratings from region to region (or the threshold at which players turn pro).
Higher rated players deciding not come, but making their decisions on other than payout. Travel distance from east & west coasts, a locale with less reputation than Charlotte, less-known courses, or other reasons.
It could be less about Emporia, and this year's payout, than Charlotte.
Not being a Pro-Am Worlds.
Of course, it could be the top-rated Ams being turned off by the payout system, too.
But I think you'd need to include more years, at various locations, to get a better idea.