Get to Know Your Credit Score

It can cost you anytime you apply for a mortgage, rent an apartment, buy homeowners insurance or even interview for a new job.

It's your credit score, yet most people don't understand what it measures or how it works, according to a recent survey by the Consumer Federation of America of Washington, D.C., a nonprofit association of some 300 consumer groups.

Only about one-third of consumers correctly understand what a credit score does, the survey found.

Simply put, a credit score is your probability of repaying a loan.

It is a predictor of your credit behavior, spun from a complex computer model and based on your credit history. That history is stored and constantly updated by the nation's top three credit reporting agencies: Equifax (EFX Quote), TransUnion and Experian, a subsidiary of the U.K.'s Gus Plc (GUSSF Quote).

The best-known credit score is the FICO from industry pioneer Fair Isaac (FIC Quote). FICO scores range from the poorest rating of 500 to a top of 850, with 723 as the nation's current median score, according to the company.

The higher the score, the more credit is available to you at lower interest rates. A borrower seeking a $300,000 mortgage with a score below 559 would pay about 9.234% interest on a 30-year fixed mortgage, or $2,465 a month, according to Fair Isaac, while the same loan would cost a borrower with a FICO above 720 just 5.515% interest, or $1,706 per month.

"Ignorance about your credit score can cost you," says Liz Pulliam Weston, author of the new book Your Credit Score: How to Fix, Improve, and Protect the 3-Digit Number that Shapes Your Financial Future and syndicated newspaper columnist. Usually people with bad or mediocre credit "get all the loans they want," she says, "but they don't realize the high price they're paying."

The use of credit scores exploded in the mid-1990s, when the nation's biggest mortgage-financing companies, Fannie Mae (FNM Quote) and Freddie Mac (FRE Quote), began requiring them, while lower interest rates prompted millions of homeowners to refinance their mortgages, according to Weston. "Once the refi boom took off," she says, "more people got obsessed with controlling and improving it."

Credit scores have helped make massive amounts of credit available to consumers. Americans now owe trillions of dollars in records amounts of debt on credit cards, auto loans and home-equity lines of credit. The ratio of household debt to disposable income has risen considerably, from 1.01 in January 2000 to a current high level of 1.20, according to the latest U.S. Commerce Department reports.