“They did the research later,” Paperno said. “The good news for FICO is the data supported it.”

The rates of default differ considerably, at least to civilian eyes. The FICO research showed 72% of those with a foreclosure later defaulted on another debt, compared with 55.1% of those with a short sale and 50.1% of those who arranged a deed in lieu of foreclosure, which means they voluntarily surrendered their keys to the bank rather than going through formal foreclosure.

So borrowers who were more proactive were significantly less likely to default than those whose homes were lost to foreclosure. Nonetheless, FICO views a one-in-two chance of default as exceptionally high risk.

“That’s pretty high,” Paperno noted. “It can be a lot lower and still not be a loan you would want to make.”

FICO hasn’t been moved in the past by arguments that things are different this time. It didn’t alter its formulas after the huge wave of foreclosures in recent years, though many more people lost their homes because of economic circumstances beyond their control. If FICO’s research shows people are more likely to default after a certain event, that event will continue to have an impact on scores.

Since FICO won’t listen to your pleas for leniency, you’ll need to take matters into your own hands to rebuild your scores. That means you should:

Defy expectations. Be among the 45% of people who don’t default after a short sale. That won’t change the initial impact of the short sale on your scores, but staying current will keep you from suffering more damage.

Use credit cards lightly but regularly. Using credit cards can help rehabilitate your scores, but you don’t need to carry a balance or pay interest. Charge small amounts to your cards and pay them off in full every month. Try to use 30% or less of your credit limits at any given time. If you don’t have a credit card, you can start with a secured card that gives you a credit limit equal to the deposit you make with an issuing bank.

Consider an installment loan. An open, active installment account, such as a student or auto loan, can help you build up your scores if you make every payment on time. If you don’t have such an account, consider taking out a small personal loan from a credit union or bank that reports to all three credit reporting bureaus.

Don’t shoot yourself in the foot. There are plenty of ways to hurt your scores inadvertently. These include closing accounts, applying for a bunch of new accounts in a short period and letting a dispute or medical bill fall into collections. If you use the diligence you applied to the short sale process to monitor your credit accounts, you should be able to restore your good scores within a few years.

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Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.

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