WASHINGTON — Average U.S. mortgage rates started the year by dipping to new lows, with the benchmark 30-year rate marking its lowest level since May 2013.

The ongoing decline in mortgage rates would appear to be a boon for prospective homebuyers. But it hasn't yet significantly enticed more buyers into the market. At the same time, there are fewer distressed properties and bargains coming onto the market that attract real estate investors.

This week the nationwide average rate on the 30-year loan fell to 3.73 percent from 3.87 percent last week, mortgage giant Freddie Mac reported. The average for a 15-year mortgage, a popular choice for people who are refinancing, slid to 3.05 percent from 3.15 percent last week.

A year ago, the 30-year mortgage stood at 4.51 percent and the 15-year mortgage at 3.56 percent. Mortgage rates have remained low even though the Federal Reserve in October ended its monthly bond purchases, which were meant to hold down long-term rates.

The housing market has struggled to fully rebound since the recession ended more than five years ago. Many potential buyers lack the savings and strong credit history needed to afford a home, causing them to rent or remain in their existing houses instead of upgrading. Higher home prices and relatively stagnant incomes have also curtailed buying.

"The key issue for first-time buyers has not been mortgage rates," said Jonathan Smoke, chief economist for realtor.com. It's been concerns like not being able to qualify for a mortgage or to put together a down payment, he noted.

Median household incomes have yet to completely recover and remain below their 2007 levels after adjusting for inflation. Limited income gains have cut into the cash flow and down payment savings needed to buy a home. Meanwhile, home prices have risen and lenders have kept standards tight for making mortgage loans.

And experts see a trend toward millennials putting off buying their first home.

The hesitation can be glimpsed in the number of Americans signing contracts to buy homes. It rose only modestly in November, according to the National Association of Realtors.

At the same time, the bulk of homeowners who could refinance appear to have already done so in recent years. With many home borrowers already carrying mortgages in the range of 3.5 percent to 4 percent, it may not be worth it for them to refinance at current rates. Refinancing carries its own costs and fees.

The picture could improve, though, as the effect of recent changes kicks in. Fannie Mae and Freddie Mac, which back the overwhelming majority of new mortgages, recently relaxed their standards for borrowers' credit scores to qualify.

And on Thursday, President Barack Obama announced a plan to reduce some mortgage insurance premiums, a move the White House says could save homeowners $900 a year and attract 250,000 first-time homebuyers.

Under the plan, the Federal Housing Administration will reduce its annual insurance premiums for first-time buyers for mortgages it backs by 0.5 percentage point, to 0.85 percent.

The changes, together with an anticipated stronger economy and improved job market this year, are a "clear positive" for the housing market, realtor.com's Smoke said

The decline in mortgage rates also has come as bond yields have hit record low levels. Mortgage rates often follow the yield on the 10-year Treasury note, which has fallen below 2 percent. Bond yields rise as prices fall.

Bond prices were an unexpected strong spot for the financial markets last year, reflecting concerns over global economic weakness.

The 10-year note traded at 1.97 percent Wednesday, down from 2.17 percent a week earlier. It recovered to trade at 2 percent Thursday morning.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country at the beginning of each week. The average doesn't include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for a 30-year mortgage was 0.6 point, unchanged from last week. The fee for a 15-year mortgage declined to 0.5 point from 0.6 point.

The average rate on a five-year adjustable-rate mortgage fell to 2.98 percent from 3.01 percent. The fee was unchanged at 0.5 point.

For a one-year ARM, the average rate slipped to 2.39 percent from 2.40 percent. The fee held at 0.4 point.