The Federal Reserve Bank of San Francisco wonders how bad mortgage default is for getting future mortgage credit.

Well, it's pretty bad.

Their research report finds that 12 years after a mortgage termination, just above 35% of borrowers with no prior defaults have taken out new mortgages. Only about 10% of borrowers with a prior serious delinquency regain access to the mortgage market within 10 years of their default.

They also compared homeowner return-to-mortgage behavior from the more-modern years of 2001, 2003 and 2008. Those who dropped out in 2008, they found, are much slower to return.

"The Great Recession that began in 2007 was much deeper than the 2001 recession, and uncertainty about jobs or future income prospects may have made people unwilling or unable to demand housing at the rate seen after previous recessions," write William Hedberg and John Krainer.

The good news is that the survey is not powerful enough to assume the mortgage termination is due to foreclosure.

"They could have moved, or adjusted their housing expenditures by trading up or downsizing. Or they could have paid down their mortgages and now own their houses outright. We might expect that most borrowers who have paid off their mortgages will never return to the market," the authors say.

Given current events, for the 2008 mortgage defaults, the above pay-off explanation feels the least likely.