Of course this is not the same, statistically, but one thing I have done in the past is to find the most ridiculously expensive property in an area, look up the tax records online, and then google the owners. It takes a bit of work, but the picture that emerges is quite interesting.

For example, I live in the Seattle area, and I know where the mega-wealthy enclaves are here. Who owns the biggest mansions? Microsoft executives, members of the Nordstrom family, members of the construction family who built the Space Needle, people connected with Daniel's Broiler, some guy who invented a new kind of eyeglasses, a congressman's ex-wife, a woman who grew and sold her IT consulting firm, a guy who built a successful condo listing website, doctors, the founder of an investment firm, a commercial real estate developer... In short, it was mainly key players in big local businesses, entrepreneurs, and a small handful of physicians.

I imagine if one did this for NYC, the picture would look predictably different.

EDIT: I forgot, the site virtualglobetrotting.com makes this easier. Hamptons example: http://virtualglobetrotting.com/map/lloyd-blankfeins-house/n...