Richard Thaler, a Professor of Economics at the Booth School of Business, University of Chicago, on the reasons why millions of homeowners under water- owing more on their homes than their homes are worth- have not defaulted in large numbers. In places like Nevada nearly two thirds of homeowners are under water. Changing a home, changing school for children, losing one's credit rating, social stigma. He points out that the costs are outweighed by the benefits of getting out of an underwater mortgage, and research has shown this is contagious once the process of defaulting has started. So once the neighbors are defaulting its much easier to do so and the proces picks up momentum, the psychic costs simply decline. So he says the result is that we may face a tsumani of strategic defaults. Professors Posner and Zingales of the University of Chicago have a proposal. Banks should be required to provide loan modifications in neighborhoods with home prices having dropped over 20%. Banks would reduce the payment by the average price reduction in the area and get in return 50% of the average gain in prices when the house is eventually sold. This requires Congress to pass legislation....