According to the Congressional Oversight Panel half the permanent mortgage modifications will redefault.
Since the HAMP launched in March 2009, servicers have completed 495,898 permanent modifications, and extended 1.6 million trials. So far, the Treasury has committed nearly $30 billion to the servicers for a program that was initially estimated to cost $50 billion.
This 495,898 is actually a low number, since over 1.3 million have applied to HAMP, but most got rejected. The rate is now closer to 75% to 80% if you include rejected applications, trial modifications that were rejected, and redefaults on permanent mortgage mods.