Americans' retirement plans have lost as much as $2 trillion in the past 15 months — about 20 percent of their value — Congress' top budget analyst estimated Tuesday as lawmakers began investigating how turmoil in the financial industry is whittling away workers' nest eggs.

The upheaval that has engulfed financial firms and sent the stock market plummeting is also devastating people's savings, forcing families to hold off on major purchases and even delay retirement, Peter Orszag, the head of the Congressional Budget Office, told the House Education and Labor Committee.

As Congress investigates the causes and effects of the meltdown, the panel pressed economists and other analysts on how the housing, credit and other financial troubles have battered pensions and other retirement funds, which are among the most common forms of savings in the United States.

"Unlike Wall Street executives, America's families don't have a golden parachute to fall back on," said Rep. George Miller, D-Calif., the panel chairman. "It's clear that their retirement security may be one of the greatest casualties of this financial crisis."

More than half the people surveyed in an Associated Press-GfK poll taken Sept. 27-30 said they worry they will have to work longer because the value of their retirement savings has declined.

Orszag indicated the fear is well-founded. Public and private pension funds and employees' private retirement savings accounts — like 401(k)'s — lost about 10 percent between the middle of 2007 and the middle of this year, and lost another 10 percent just in the past three months, he estimated.

Private retirement plans may have suffered slightly more because those holdings are more heavily skewed toward stocks, Orszag added.

"Some people will delay their retirement. In particular, those on the verge of retirement may decide they can no longer afford to retire and will continue working," Orszag said.

A new AARP study found that because of the economic downturn, one in five workers 45 and older has stopped putting money into a 401(k), IRA or other retirement savings account during the past year, and nearly one in four has increased the number of hours he works. More than one-third of these workers have considered delaying retirement, according to the study, which also found that more than half now find it difficult to pay for basic items such as food, gas and medicine.

The hearing came just as workers are receiving — or about to receive — their quarterly retirement savings account statements, which are likely to show disheartening drops in the value of holdings.

Jerry Bramlett, the head of BenefitStreet Inc., a retirement savings plan administration company, said there's a risk that people will overreact to the bad news by pulling their money out of the accounts, which could add to their potential losses.

"For participants with many years of retirement, a drastic abandonment of equity positions in their retirement account will only serve to lock in as-of-yet-unrealized losses. Markets do go up and down, and 401(k) participants must try to think long-term," Bramlett said.

Still, he said workers should do their best to diversify their retirement savings accounts and "perhaps consider less volatile investments."

On the heels of enacting a $700 billion market bailout, lawmakers are searching for ways to help workers who are feeling the ripple effects of the financial crisis.

"What should we be doing to try to find a way to salvage the retirement position of American workers?" said Rep. Dennis Kucinich, D-Ohio, an opponent of the government rescue plan. Congress, he added, "rushed to protect Wall Street in hopes that some benefits would trickle down to workers."

The massive losses have already reopened a bitter and long-running debate about what role — if any — the government should play in helping workers save for retirement.

Some experts argue that the hefty tax subsidies that Congress has put in place in recent decades for 401(k) and other worker-contribution accounts have made people's retirement income less secure by shifting risks, decisions and costs from employers to people who often know little about investing.

"They are fatally flawed," Teresa Ghilarducci, an economist at the New School for Social Research, said of the tax-advantaged plans. "They're too risky, and it's not good policy to have workers run their own retirement plan. They want government help."

Common mistakes workers make include overinvesting in a single stock — often their company's — and participating in funds that carry large fees or involve excessive risk, the witnesses said.

"You cannot tell the participants at the bottom of your fund prospectus, 'Warning: Your psychology may lead you to make irrational choices,'" said Christian E. Weller of the University of Massachusetts Boston.

The current market turmoil adds to an already difficult retirement savings picture for Americans, who are increasingly shouldering the burden of managing and funding their own company-sponsored retirement savings plans as firms eliminate traditional pensions.

Even before the recent downturn, older Americans were on track to continue working longer. Twenty-nine percent of people in their late 60s were working in 2006, up from 18 percent in 1985, according to the Bureau of Labor Statistics. Over the next decade, the number of workers who are 55 and older is expected to increase at more than five times the rate of the overall work force, the BLS reported.

Falling home values and now the decimation of much of their savings could plunge older Americans into period of austerity not seen in decades, Miller said: "The fear factor is huge, and they don't see the availability of resources to them to get well."

Orszag said the situation has little precedent in American history.

"The period that we're experiencing is arguably the greatest collapse in confidence that we've experienced since the Great Depression," he said.