America has a long and undistinguished history of populist politicians stacking the cards against lenders and in favor of risky homeownership. Proving that good intentions are no guarantee of good policy, President Jimmy Carter's 1977 Community Reinvestment Act, which required banks to make loans to low-income people, was just another legislative leg-up for high-risk borrowers. If socially laudable but economically reckless laws cause entirely predictable problems for lenders, don't be surprised if taxpayers have to bail them out.

The final proof that American social policies have made mortgage lending an unviable industry rests with Fannie Mae and Freddie Mac. If sensible business people don't get into the mortgage industry because it is fundamentally a bad business, the American way has been to send in a couple of quasi-government agencies to fill the gap.

Fannie and Freddie dominated the mortgage industry because ultimately government was prepared to fund activities that prudent lenders would not. When their implicit government guarantee became explicit, America's system of government-directed lending on socially desirable, but commercially imprudent, lending stood exposed.