George Mason University economics professor Russell Roberts writes in today’s Wall Street Journal:

Beginning in 1992, Congress pushed Fannie Mae and Freddie Mac to increase their purchases of mortgages going to low and moderate income borrowers. For 1996, the Department of Housing and Urban Development (HUD) gave Fannie and Freddie an explicit target — 42% of their mortgage financing had to go to borrowers with income below the median in their area. The target increased to 50% in 2000 and 52% in 2005.

For 1996, HUD required that 12% of all mortgage purchases by Fannie and Freddie be “special affordable” loans, typically to borrowers with income less than 60% of their area’s median income. That number was increased to 20% in 2000 and 22% in 2005. The 2008 goal was to be 28%. Between 2000 and 2005, Fannie and Freddie met those goals every year, funding hundreds of billions of dollars worth of loans, many of them subprime and adjustable-rate loans, and made to borrowers who bought houses with less than 10% down.

Fannie and Freddie also purchased hundreds of billions of subprime securities for their own portfolios to make money and to help satisfy HUD affordable housing goals. Fannie and Freddie were important contributors to the demand for subprime securities.

Fannie and Freddie played a significant role in the explosion of subprime mortgages and subprime mortgage-backed securities. Without Fannie and Freddie’s implicit guarantee of government support (which turned out to be all too real), would the mortgage-backed securities market and the subprime part of it have expanded the way they did?

Perhaps. But before we conclude that markets failed, we need a careful analysis of public policy’s role in creating this mess. Greedy investors obviously played a part, but investors have always been greedy, and some inevitably overreach and destroy themselves. Why did they take so many down with them this time?

Part of the answer is a political class greedy to push home-ownership rates to historic highs — from 64% in 1994 to 69% in 2004. This was mostly the result of loans to low-income, higher-risk borrowers. Both Bill Clinton and George W. Bush, abetted by Congress, trumpeted that rise as it occurred. The consequence? On top of putting the entire financial system at risk, the hidden cost has been hundreds of billions of dollars funneled into the housing market instead of more productive assets.

Beware of trying to do good with other people’s money. Unfortunately, that strategy remains at the heart of the political process, and of proposed solutions to this crisis.