If it weren’t for Atherton’s zoning code, you’d never be able to buy that mansion for a mere $6m. A developer that wanted to tear it down and build condos could bid far more than that. But the zoning code mandates single-unit buildings with a floor area ratio below 18% on lots of at least 1 acre, so $6m it is. Quite the bargain.

Now and again, somebody manages to cobble together rent for an Atherton mansion by forming an ad-hoc commune, but generally speaking, the zoning code is working exactly as intended: the people that live in Atherton determine the zoning that determines who gets to live in Atherton, so the process perpetuates itself.

And this comes at the expense of people who want to buy condos or rent apartments. Since so few are available, and the market allocates them to the people with the deepest pockets, only people with deep pockets can buy or rent an apartment in the mid-Peninsula.

The case of Atherton is, of course, extreme. Atherton has the highest median household income of any city in the nation. Of course it’s going to be an elitist sort of place.

The same effect happens in San Francisco, too, though. Here’s three ways a similar 25' wide lot (standard in the Western Neighborhoods) can be used: a 1 unit building, a 5 unit building, and a 24 unit building.