In the world of home mortgage lending, one of the biggest changes in recent years has been the advent of a "risk-based" pricing model. You are likely to qualify for a more or less attractive rate based largely on the risk the lender feels there is of you failing to pay on time.

While the traditional income-to-debt ratios are still calculated using the projected mortgage payment as a percentage of your income, and although overall monthly debt obligations are still taken into consideration, these factors carry less weight today in making loans.

In their place, mortgage lenders are relying more on a three-digit number known as your credit score. It is derived strictly from information contained in your credit report. You can think of it as a combination of all your credit experience and performance in the past decade squeezed into a number.

That number makes it extremely easy for lenders to gauge the degree of risk they have associated with not only each loan in their portfolio, but the likelihood that each individual loan will be paid on time.

Lenders consider this number a critical part of any loan application and have begun relying on it more as time has shown that such numbers accurately reflect credit habits.

A single company, called Fair, Isaac & Co., generates credit scores for lenders based solely on data in your credit report. Because there are three major credit repositories, you have three different credit reports, so you always have three credit scores. Lenders typically discard the top and bottom scores and focus exclusively on the middle score.

Fair, Isaac & Co. predicts that if your score is above 800, the likelihood of serious delinquency is 1 in 1,292. If it is between 700 and 719, that likelihood jumps to 1 in 123. If your score is below 600, the likelihood of serious delinquency or foreclosure is 1 in 8.

Under Georgia law, your credit report is available to you free of charge twice a year. Call Equifax at 1-800-685-1111, TransUnion at 1-800-422-4879 or Experian at 1-800-888-4213. Although these firms make it difficult to obtain your free report, you can succeed if you are persistent.

But credit scores are considered an "interpretation" of your report, so these numbers cannot be ordered for free. Perhaps the easiest place to see all three of your scores and credit reports at one time is the Fair, Isaac site at www.myfico.com. While the fee of $39 seems excessive, its score simulator allows you to see your score under various "what if" scenarios, a very helpful feature.

Most home mortgage lenders will pull your credit reports and get your three credit scores. That creates an "inquiry" on your report, which can lower your score by up to two points. That's why it's wise to give your Social Security number to lenders when you are simply shopping for rates and loan programs. It's better to tell them your score and avoid the inquiry.

Fair, Isaac refuses to release detailed information about what patterns of behavior its computer looks for in the very best consumers, claiming only that you should pay bills promptly and use credit wisely. But the weight given to certain credit actions and number of points charged for inquiries and applications remains a mystery, which the company makes no effort to explain.

Because we know your score is derived solely from information in your credit file and because that file can be obtained free, it is important that you make sure the information is accurate. It's easy for inaccurate information to creep into your file and that can hurt your score.

According to Experian, the average score nationally is 677, while the current average in Georgia is a disappointing 667. The middle score that qualifies you for the best home mortgage rates and terms is around 720, depending on the program, and at that level, your credit is almost squeaky-clean. You can compare how you match up at www.nationalscore.com.

Major factors included in figuring your score include current debt, credit usage and minimum monthly payments. Additional elements are open credit cards, late payments and authorized merchant inquiries.

My advice is to check all three reports at least six months before you hope to buy. Creditors move quite slowly to correct mistakes, and then it takes time for the correct information to make it to your report. For additional information, you can go to my Web site at www.money99.com and click on "Additional Resources," then download the free "Credit Scoring Booklet."

 John Adams is a broker and investor in metro Atlanta.