In the Bay Area, almost three- quarters of mortgage loans taken out last year allowed borrowers to delay the payment of principal and, in some cases, interest, according to data from San Francisco research firm LoanPerformance. 

Nearly 43 percent of new mortgages — including those to purchase or refinance a home — were interest-only loans, which are adjustable-rate mortgages that require no principal payments for a set number of years. That’s roughly the same percentage as in 2004, but double the percentage as in 2003.

More surprising: So-called option ARMs jumped to 29 percent of the Bay Area mortgage market from less than 10 percent in 2004.