Mortgage rates are now lower than they were in the early 1950s. The average rate reached 4.08 percent for a few months back then, according to the National Bureau of Economic Research. Mortgages at that time typically lasted only 20 or 25 years.

Super-low rates haven’t been enough to lift the housing market, which has struggled in recent years with anemic sales and declining home prices.

Rates have been below 5 percent for all but two weeks in the past year. Yet sales of previously occupied homes this year are on track to be among the worst in 14 years.

And homeownership has dropped over the past decade by the greatest amount since the Great Depression, according to 2010 census data released Thursday.

“There’s nothing to gloat over,” said Sal Guatieri, a senior economist at BMO Capital Markets in Toronto. “The record low interest rates are a reflection of the times. The U.S. economy is fragile and the global economic head winds remain brisk.”

Total mortgage applications fell more than 4 percent this week from the previous week, according to the Mortgage Bankers Association. Refinancing applications declined more than 5 percent.

“Considering how far mortgage rates have fallen, we’d expect to see more people refinancing and buying,” said Celia Chen, director of housing economics at Moody’s Analytics. “It’s still the lack of jobs and the difficult credit environment that’s pushing most people away.”

For many Americans, buying a house is too big a risk in this economy. Unemployment is above 9 percent, raises are scarce and millions of foreclosures are forcing down home prices.

Others can’t qualify for the historically low rates. Banks are insisting on higher credit scores. And many want first-time buyers to put down 20 percent. Few people have that much cash or home equity to satisfy the requirement.

“There’s a huge pile of applications we’re rejecting because of low credit scores. It’s been that way for years,” said John Stearns, a senior mortgage banker at American Fidelity Mortgage outside of Milwaukee.

Mike Anderson, a mortgage broker in Baton Rouge, La., said the low rates haven’t changed the obstacles preventing people from getting loans. Most are without a job, have bad credit or are have negative home equity. Any one of those is a deal-breaker.

“Same new lows, same problems,” Anderson said. “You can get people with 800 credit scores that you have to turn away.”

Mortgage rates have tumbled because they tend to track the yield on the 10-year Treasury note. The yield has fallen in recent weeks, largely because investors are worried about the U.S. economy and the debt crisis in Europe. So they have shifted their money out of stocks and into the relative safety of Treasurys.

And rates could fall even further now that the Federal Reserve has started shuffling its investment portfolio to try to lower long-term rates.

A drop in mortgage rates could help the economy if more people can refinance. When people refinance at lower rates, they pay less interest on their loans and have more money to spend.

Consider a homeowner who owes $250,000 and is paying 5.09 percent on a 30-year fixed mortgage. That was the average rate being offered in January 2010. Refinancing the loan at 3.94 percent could save the homeowner more than $2,000 a year.

But most people who can afford to refinance have already locked in rates below 5 percent.

Economists say rates need to fall at least a full percentage point before it makes sense to refinance again. That’s because homeowners typically pay a few thousand dollars in closing costs when they refinance.

The low rates being offered also don’t include extra fees, known as points, which many borrowers must pay to get the best rates. One point equals 1 percent of the loan amount.

Once extra fees are added in, the effective average rate on the 30-year loan is 4.12 percent, Freddie Mac said.

Many lenders are cutting these fees to entice more people to refinance. And others are simply offering better rates.

Zillow.com, a real-estate website that offers mortgage-rate quotes from lenders, has recorded average rates on the 30-year loan below 4 percent for five straight weeks.

That’s because the site allows lenders to compete with each other.

“This is an opportunity most people won’t see again in their lifetimes,” said Stan Humphries, Zillow’s chief economist. “But we’re in a period where rates are going to stay pretty low for a while because it’s going to take some economic growth to bring rates up again.”

Associated Press reporters Marcy Gordon and Dan Wagner contributed, and material from Bloomberg News is used in this report.