The real estate sales website on Monday reported that nearly a third of Americans are unlikely to qualify for a mortgage because their credit scores are too low.

The report said that prospective borrowers with a credit score under 620 have been effectively excluded from the mortgage market. Zillow, quoting data from, 29.3% of Americans have credit scores of less than 620. Applicants on in that group were unlikely to receive even one loan quote, even with downpayments of 15%-25%.

Conversely, the best interest rates went to those with the highest credit scores (720+), which comprised 47% of the total applicants. Borrowers with credit scores of 720 or above got an average lowest quote of an annual percentage rate of 4.3% for conventional 30-year fixed mortgages. Borrowers with mid-range credit scores between 620 and 719 received APRs between 4.73% and 4.44% percent, with the APR rising as credit score drops. Those with credit scores below 620 received too few loan quotes to calculate average low APR.

"We are in an era of historically low mortgage rates, reaching levels not seen in decades," said Zillow Chief Economist Dr. Stan Humphries. "Coupled with four years of home value declines, homes are more affordable than we've seen for years. But the irony here is that so many Americans can't qualify for these low rates, or can't qualify for a mortgage at all. Four years ago, in the era of easy-to-get subprime loans, many borrowers with low scores did buy homes, which in turn helped contribute to a housing bubble. Today's tighter credit is a predictable response by banks after the foreclosure crisis, but also keeps a cap on housing demand, which is important for the greater housing market recovery."

The report was based on an analysis of more than 25,000 loan quotes and purchase requests made on the Zillow Mortgage Marketplace during the first half of September.

Zillow Mortgage Marketplace receives more than 300,000 loan requests each month from borrowers, who can anonymously request mortgage quotes from hundreds of lenders across the country. Lenders then submit loan quotes customized to each borrower's financial situation. The analysis examined number of quotes and average lowest APR for 30-year fixed, conventional mortgages that were quoted to borrowers who intended to purchase a home with down payments between 15% and 25%, along with credit score information from