The U.S. economy is in the midst of an old-style credit crunch brought on by a combination of bad policies and incredibly lax underwriting standards at financial institutions. The biggest policy failure was the decision by Alan Greenspan’s Federal Reserve to hold interest rates too low for too long. That led to a tsunami of credit that inundated the economy with cheap money. Mortgage lenders in particular were flush with funds and searched for deals wherever they could be found. Heretofore unqualified borrowers suddenly “qualified” as underwriting standards relaxed and then disappeared.

Egged on by statements from Chairman Greenspan, market participants came to believe the era of low interest rates would last indefinitely. But the era did come to an end as the Fed was forced to begin raising interest rates. Faced with the prospect of paying higher rates on their mortgages in the future, borrowers began defaulting. First home prices stopped rising, and then home prices began dropping — precipitously in some overheated housing markets. Now we are approximately six months into a new cycle of lower interest rates, but with no end in sight to the crunch.

At least two other factors stoked the crisis. First, many exotic financial products were issued whose value was tied in one way or another to home prices and the value of the securities into which home mortgages were bundled, such as collateralized mortgage obligations. The pricing of these financial products was the product of complex economic models, not the outcome of market transactions. As the value of the underlying homes and mortgages declined, pricing of the financial exotica became nearly impossible. As we learned in the collapse of Long Term Capital Management, these pricing models fail precisely when their accuracy is most important — in times of financial turbulence. The inability to price the financial products has exacerbated losses among the firms holding them.

There is a wonderful parallel here to the collapse of the Soviet Union. As the great Austrian economist Ludwig von Mises argued almost 100 years ago, central planning inevitably fails because there are no market prices to allocate resources. Market prices can only be the outcome of actual market transactions among buyers and sellers. Planners used mathematical formulas to value resources, especially capital. Now Wall Street wizards have imported Soviet thinking to allocate financial capital. Is it any wonder that it failed?

The second factor contributing to the housing market collapse was the federal government’s commitment to “affordable housing.” Lenders, especially Fannie Mae and Freddie Mac, were pressured into promoting housing to low-income groups that could not qualify for normal loans. That policy is predicated on the belief that there is an underserved group of people who, but for economic discrimination or some other market failure, would be homeowners. That social goal and the credit-driven desire for more deals merged into mortgages made without adequate collateral.

We learned two lessons from the drive to make home ownership available to the heretofore underserved. First, many of these were not homeowners because they could not afford a home. Only under the temporary “hothouse” conditions in mortgage markets did they seem to qualify. Second, people who have no equity in their homes cannot meaningfully be said to be owners. When times turn tough, they will walk away. They were effectively renters, not homeowners.

The crisis will end when housing markets hit bottom and the prices of mortgage securities stabilize. Banks also need to unwind their positions in exotic financial derivatives.

The Fed needs to understand it is facing a capital crisis, not a liquidity crisis. The very low interest rates on safe assets show there is ample liquidity in financial markets. The Fed should not supply capital. That is the job of markets, and they are doing it.