From Jan Hatzius, Goldman Sachs chief US economist, presented at the Brookings conference, Beyond Leveraged Losses: The Balance Sheet Effects of the Home Price Downturn. Here is a short excerpt on estimating mortgage credit losses (note that Goldman is now forecasting prices to decline another 10%):
If nominal home prices remain at their 2008 Q2 level until mid-2009, before reverting to a +3% annualized trend, our model implies that mortgage credit losses realized in the 2007-2012 period will total $473 billion. If nominal home prices fall another 10% through the middle of 2009, the model projects losses of $636 billion. Finally, if prices drop another 20%, predicted losses increase to $868 billion. Moreover, the table suggests that losses peak in the third quarter of 2008 if home prices are flat going forward; in the fourth quarter of 2008 if prices drop another 10%; and in the second quarter of 2009 if prices drop another 20%.