(For an updated version of this working paper, see WP 10-06.)
How did investors holding assets backed by subprime residential mortgages react when Treasury Secretary Paulson announced the so-called "teaser freezer" plan to modify mortgages in December 2007? We apply event-study methodology to the ABX index, the only source of daily securities prices in subprime mortgage markets. Our results show investors in the ABX initially perceived that the plan would improve conditions in the subprime housing markets, but results from a longer event window show this positive effect was swamped by continued deterioration in housing markets. The positive effects of the plan disappear for junior tranche securities in recent vintages, consistent with poorer quality collateral pools.