Some families do have other income. Just under half of those families expect pension income of a median $26,500 a year. Added to the $9,073 in 401k income, that still falls short. Some families have other savings, but Federal Reserve and other data suggest that they don't fill the gap for most people.

These data don't even include those in the direst situations: People who have lost their jobs, stopped contributing to 401k plans or shifted to jobs without 401k plans. The numbers also don't account for inflation, which would further eat into income from a 401k.

Some researchers question the Fed numbers because they are based on surveys rather than on records of actual contributions.

Jack Van Derhei, head of research at the Employee Benefit Research Institute, a group supported by 401k providers, estimates the median American actually has about $158,754, based on data from 401k providers. That assumes an individual 60 or older who has been at the same company for more than 30 years -- a somewhat different demographic from the one the Fed data measured.

Even the higher median 401k amount generates much less income than what is needed.

The 2007-2009 financial crisis worsened the difficulties. Since the housing and financial markets began to collapse, about 39% of all Americans have had their homes foreclosed on, lost their jobs, gotten underwater on a mortgage or fallen more than two months behind on their mortgage payments, says Michael Hurd, director of the Rand Center for the Study of Aging.

Pushed off the track

In 2008, when he was 59, John Mastej figured he was on track to retire in his early 60s. He and his wife both were working, with 401k plans. Counting all their savings, they had close to $200,000. Mastej was putting 20% of his salary into his 401k.

The financial collapse cut their savings in half and left Mastej out of work for two years, with no 401k contributions. He had to dip into other savings and use up an inheritance to pay the mortgage. He found a new job in a specialty food store, but it paid much less than his old one in a plastics factory.

Today, Mastej figures he has about $90,000 in savings left, including about $50,000 from the two 401k accounts, now mostly in a fixed annuity that isn't affected by the stock market. He and his wife have canceled their satellite television subscription and drive 11-year-old cars to work.

They buy some food at discounted prices through their church, but are proud they have remained current on their mortgage, home equity loan, insurance and property taxes.

"We don't go out to dinner. We don't do much entertaining," Mastej says. "I will probably end up having to work for another 10 years."

Carol Dailey is still working at age 71. Dailey spent 10 years as an executive assistant at America Online and had stock options she estimates were once worth $1.7 million. The options' value collapsed with the company's stock.

Now she relies on her 401k, which took a hit in the 2008 market plunge. She has cut back spending for entertainment and organic food, and continues to work three days a week as an office manager for an Internet security company.

"(When I was at) AOL, we were buying $60 bottles of wine and not blinking. Now I drink box wine," she says.

Click here to become a fan of MSN Money on Facebook

Eventually, Dailey wants to retire completely. Then, to make ends meet, she plans to take bigger investment risks. Her financial adviser will shift some of her savings out of an annuity and into high-yield bonds and real estate investment trusts, aiming to double the return on that money to 10% a year.

Some people were done in by the twin collapses of the housing and stock markets.

Patti and Bob Webster had accumulated a six-figure balance in their 401k accounts and were building a dream house in North Carolina in 2007. They planned to retire there in about a year. Then their builder went out of business, and the stock crash knocked 40% off their savings. They temporarily suspended 401k contributions.

"We thought we had the perfect plan," says Patti Webster. "When the bottom fell out of the market, it kind of fell out of our perfect plan as well."

Today in their mid-60s, they have completed the house but have worked two years longer than planned and expect to work two years more. "We are having to spend another two years in just trying to catch up with what the market did to us," Webster says.

This article was reported by E.S. Browning for The Wall Street Journal.