Watching "P"s and "Q"s

Here's a letter sent earlier this week to the New York Times:

Paul Krugman rightly writes that housing prices "rose sharply only where zoning restrictions and other factors limited the construction of new houses.  In the rest of the country – what I [Krugman:] once dubbed Flatland – permissive zoning and abundant land make it easy to increase the housing supply, a situation that prevented big price increases" ("Georgia on My Mind," April 12).  But his conclusion that this situation, where it...