Harvard economist Edward Glaeser has a different explanation of the census results than the tax-driven one I have been offering here. He says the answer is the "obscure rules regulating local land use":
In a sense, the anti-regulation crowd is right that the laissez-faire attitude of the South and West explains their recent growth. But the usual argument focuses on the wrong regulations.
Housing regulations, more than those that bind standard businesses, explain the Sun Belt's population growth. If New York and Massachusetts want to stop losing Congressional seats, then they must revisit the rules that make it so difficult to build.
Link via Mankiw.