Metro Atlantans are not deadbeats, as a rule. But a recent study suggests that we are relatively poor credit risks.

Among the 20 most populous metropolitan areas, Atlanta has the 16th-best average credit score, according to Experian, one of the big three credit rating agencies.

The average score of Atlantans in Experian's most recent survey was 670. That is slightly under the national average, 678, and considerably lower than the leading city, Minneapolis, which averaged 707. Dallas was the tail-ender, with an average of 653.

Experian's system yields scores from 330 to 830. Bigger is better.

"Credit scores have to do with [getting] good credit rates and loan terms," said Heather Greer, an Experian spokeswoman. "You want to be above 720. Over 700 is good; over 720 you'll be getting the best rates."

A credit score, in essence, is an attempt to estimate how likely you are to repay your debts.

There are scads of scoring systems, many of them growing out of the well-known FICO score developed by California-based Fair Isaac Corp. Experian and its main competitors, Atlanta's Equifax and Pennsylvania-based TransUnion, may tweak the FICO formulas to develop their own credit scores. Banks and other lenders often make further refinements to match their particular needs.

Your number could differ from one rating system to the next, but in general you can expect them all to give a similar indication of your creditworthiness.

Credit scores confuse many people. One recent survey from a TransUnion subsidiary found that about 40 percent of Americans know nothing at all or not very much about their credit scores.

But they are certainly important. "Most consumers want to have credit cards, or buy a car or a house, or get a job," Greer said. "Most if not all of these financial institutions and employers are starting to look at your credit scores to see how risky you are."

A very low score could scare off all credit card companies and all mortgage lenders.

In addition, higher scores generally lead to lower interest rates, because lenders have more confidence that high-scoring people will pay their debts.

You can check out the interactive tool at www.myfico.com/LoanCenter to see how much difference your scores make. These numbers are based on the FICO scoring system, and run from 300 to 850.

At the middle of last week, for example, an Atlantan with a middling score of 550 would have had to pay 6.98 percent for a 30-year fixed-rate mortgage. Bump the score up to 600, and the average offer was 6.51 percent. At about 700, the average levels off at 5.9 percent.

Bankrate.com, the source of all this data, showed an even more extreme advantage if you look at the lowest offers, rather than the average ones. They range from 6.98 percent for credit scores of 500 to 5.52 percent for those with scores of about 650 and higher.

In the Experian survey, average scores in Atlanta were driven down by two main factors: late payments and relatively high rates of credit utilization.

Credit utilization refers to how much you have borrowed, compared to how much borrowing power you have. Atlantans used 26.7 percent of available credit in February, the latest available data. For example, if you had one credit card with a $10,000 limit and you owed $2,670 on that account, your utilization would be exactly at the 26.7 percent average.

It's important, Greer said, because a relatively high percentage makes lenders wonder whether you're living beyond your limits.

Atlantans made about 10 percent more late payments than the national average. The numerical difference is small: 0.78 percent past-due payments nationally, compared with 0.85 percent in Atlanta. But the impact on lenders' confidence is large.