But on the other hand, we have another economist.

Problems in mortgage lending go “well beyond subprime,” and the tightening of loan underwriting standards now underway is likely to push demand for homes down 15 percent and depress prices by 5 percent this year. According to a report issued Tuesday by Banc of America Securities LLC, “Dissecting the Mortgage Distress,” there’s already an excess supply of 800,000 existing homes on the market, and another 300,000 will soon be added to inventories through foreclosure.

But the biggest problem facing housing markets may be the tightening of credit that’s taking place as lenders put the brakes on risky loans including low-documentation and zero-down-payment mortgages, the report said.

“We expect loans with a combination of low FICO scores and high (loan-to-value ratios) will end or tighten with many buyers choosing to remain as renters,” wrote BAS analyst Daniel Oppenheim. BAS is a subsidiary of Bank of America Corp.

The mortgages most likely to disappear are those with loan-to-value ratios of 98 percent or more and with FICO scores of 680 or less. Those loans, which accounted for 12 percent of home purchases in 2006 and 77 percent of delinquencies, “likely won’t be seen again for some time,” Oppenheim predicted.

Nearly half of loans awarded in 2006 with FICO scores of 680 or less and loan-to-value ratios of 98 percent or more had no or limited documentation, “which is worrisome to say the least,” the report said.