I highly recommend reading the whole paper but here is part of the conclusions from the paper (emphasis added):
Since we conclude that contract frictions in securitization trusts are not a significant problem, we attempt to reconcile the conventional wisdom held by market commentators, that modifications are a win-win proposition from the standpoint of both borrowers and lenders, with the extraordinarily low levels of renegotiation that we find in the data. We argue that the data are not inconsistent with a situation in which, on average, lenders expect to recover more from foreclosure than from a modified loan. At face value, this assertion may seem implausible, since there are many estimates that suggest the average loss given foreclosure is much greater than the loss in value of a modified loan. However, we point out that renegotiation exposes lenders to two types of risks that are often overlooked by market observers and that can dramatically increase its cost. The first is “self-cure risk,” which refers to the situation in which a lender renegotiates with a delinquent borrower who does not need assistance. This group of borrowers is non-trivial according to our data, as we find that approximately 30 percent of seriously delinquent borrowers “cure” in our data without receiving a modification. The second cost comes from borrowers who default again after receiving a loan modification. We refer to this group as “redefaulters,” and our results show that a large fraction (between 30 and 45 percent) of borrowers who receive modifications, end up back in serious delinquency within six months. For this group, the lender has simply postponed foreclosure, and, if the housing market continues to decline, the lender will recover even less in foreclosure in the future.
We believe that our analysis has some important implications for policy. First, “safe harbor provisions,” which are designed to shelter servicers from investor lawsuits, are unlikely to have a material impact on the number of modifications and thus will not significantly decrease foreclosures. Second, and more generally, if the presence of self-cure risk and redefault risk do make renegotiation less appealing to investors, the number of easily “preventable” foreclosures may be far smaller than many commentators believe.