Congress is contemplating a serious tightening of regulations to make the new forms of lending more difficult. New research from some of the leading housing economists in the country, however, examines the long history of mortgage market innovations and suggests that regulators should be mindful of the potential downside in tightening too much.

A study conducted by Kristopher Gerardi and Paul S. Willen from the Federal Reserve Bank of Boston and Harvey S. Rosen of Princeton, Do Households Benefit from Financial Deregulation and Innovation? The Case of the Mortgage Market (National Bureau of Economic Research Working Paper 12967), shows that the three decades from 1970 to 2000 witnessed an incredible flowering of new types of home loans. These innovations mainly served to give people power to make their own decisions about housing, and they ended up being quite sensible with their newfound access to capital.

These economists followed thousands of people over their lives and examined the evidence for whether mortgage markets have become more efficient over time. Lost in the current discussion about borrowers’ income levels in the subprime market is the fact that someone with a low income now but who stands to earn much more in the future would, in a perfect market, be able to borrow from a bank to buy a house. That is how economists view the efficiency of a capital market: people’s decisions unrestricted by the amount of money they have right now.

And this study shows that measured this way, the mortgage market has become more perfect, not more irresponsible. People tend to make good decisions about their own economic prospects. As Professor Rosen said in an interview, “Our findings suggest that people make sensible housing decisions in that the size of house they buy today relates to their future income, not just their current income and that the innovations in mortgages over 30 years gave many people the opportunity to own a home that they would not have otherwise had, just because they didn’t have enough assets in the bank at the moment they needed the house.”

Of course, basing loans on future earnings expectations is riskier than lending money to prime borrowers at 30-year fixed interest rates. That is why interest rates are higher for subprime borrowers and for big mortgages that require little money down. Sometimes the risks flop. Sometimes people even have to sell their properties because they cannot make the numbers work.