So wikipedia says there are $6.1 trillion in MBS securities. Case-shiller says home prices fell last quarter 15.3% Since mortgages are backed by the actual real estate, which is rapidly decreasing in value, would we not see some correlation between falling home prices and falling MBS values (leading to write-downs)? Obviously the correlation is not 100%, but if this is any positive correlation, there are going to be billions in write-downs until the housing market stabilizes. Food for thought. Anyone know the total amount of subprime and Atl-A loans outstanding?