Even as the choice of loans continues to grow, homeowners remain fixated by fixed-rate mortgages.

With fixed rates so low, it's not surprising that borrowers want to lock in. A new study of data from the Federal Housing Finance Board shows that 82 percent of mortgages in 2003 were fixed-rate products vs. 18 percent that were adjustable.

"The fixed-rate mortgage is a cornerstone of the U.S. housing finance system and has been instrumental to the accrual of wealth on the part of many households. The low interest rates of the past two years have increasingly lured consumers seeking a predictable payment in an uncertain economy," said Stuart Gabriel, director of the University of Southern California Lusk Center for Real Estate.

The 30-year, fixed-rate mortgage is about 70 years old. The loan instrument was first offered in the 1930s after the Federal Housing Administration was created as part of financial reforms to combat the Depression.

Before that, most residential loans were balloons, requiring a payoff within 10 years. Also, mortgages were made for only up to 50 percent of a property's value.

Long-term loans took off in the housing boom after World War II, when Federal Housing Administration and Veterans Administration mortgages fueled construction in suburbs. At the same time, homeownership rates jumped after the 30-year loan became available, from 44 percent in 1940 to 65 percent in 1966. The rate is 68 percent today.

In 2003, about two-thirds of U.S. mortgage debt was in fixed-rate instruments, Gabriel told the Homeownership Alliance, an education and lobbying group made up of real estate, mortgage and consumer organizations.

Adjustable-rate loans mostly come into play when interest rates are high or rising quickly. Since adjustable rate mortgages became widely available in 1981, their share of the market has varied from a high of 39 percent in 1994 to a low of 12 percent in 2001, Gabriel found.

"Clearly, borrowers benefit from the availability of a wider variety of products. ARMs appeal to more mobile households, home buyers who expect their incomes to be positively correlated with interest rate fluctuations and buyers who are down-payment constrained," Gabriel said.