by Calculated Risk on 9/13/2009 01:11:00 PM

Kenneth Harney discusses the credit impact of various mortgage choices: Mortgage problems are walloping Americans' credit scores

For example, loan modifications that roll late payments and penalties into the principal debt owed on the house can actually increase borrowers' scores modestly. Refinancings of underwater, negative-equity mortgages ... may have little or no negative effect on scores ...

However:

... short sales can trigger big drops in credit scores. ... strategic defaults [lead to even larger credit hits] "plus negative marks on their credit bureau files for as long as seven years." ... People who file for bankruptcy protection covering all their debts (mortgage, credit cards, auto loans, etc.) will get hit [the hardest]. Bankruptcies remain on borrowers' credit bureau files for 10 years.

Harney has some data on the sharp overall decline in credit scores.

Most of these changes -- fewer people with excellent credit, more people in the lowest brackets -- have been caused by late payments on home mortgages, serious delinquencies, short sales and foreclosures ...

One of the tragedies of the housing / credit bubble was that many people bought homes before they were financially ready - or bought homes they could not afford. Now many of these people will be soured on the home buying experience, and their credit scarred for years.

And there will also be another group of people who make their payments, and keep their "excellent" credit scores, but will be stuck with their underwater homes for years.