There is an interesting website published by HUD in Washington that posts research on the impact of regulation on the cost of housing.

Here is the url:

http://www.huduser.org/rbc/search/number.asp

See following quote:

By reducing development costs by as much as 35 percent through the removal of affordable housing barriers, millions of American families will be able to buy or rent suitable housing that they otherwise could not afford.

The url is:

http://www.hud.gov/initiatives/affordablecom.cfm

NB: many of the links are no longer active. I will try to post the ones that I think are most interesting.