WASHINGTON — The economy is moving in reverse faster than the government can measure.

The contraction in the fourth quarter of 2008 had been estimated at 3.8 percent just a month ago. The Commerce Department raised it to an astonishing 6.2 percent yesterday — the largest revision since the government started keeping records in 1976.

It was the economy's worst showing in a quarter-century and raises the prospect that the nation could suffer its worst year since 1946.

"Consumers are just hunkering down and saying 'game over,' and businesses in response are cutting back on investment and employment," said Brian Bethune, an economist at IHS Global Insight. "It's a negative feedback loop."

Now in its second year, the recession is expected to stretch at least through the first six months of 2009, as shoppers slash spending in the shadow of hard times at home and aboard.

Companies, in turn, are cutting jobs and production, and resorting to other cost-saving measures to survive.

The biggest culprit behind the record-breaking revision: Businesses actually cut inventories instead of building them as the government thought they would. That reduced economic activity.

In addition, consumers pulled back even more on their spending — spending that accounts for about 70 percent of national economic activity. U.S. exports suffered a bigger drop and businesses retrenched further.

Many economists have lowered their forecast for this year's gross domestic product to show a deeper contraction of at least 2 percent. GDP, the value of all goods and services produced in the United States, is the best barometer of the country's economic health.

White House press secretary Robert Gibbs said the latest GDP figure "underscores the urgency with which the president feels we have to move to improve our economy."

The economy has not suffered a decline over a full year since 1991, and that was just by 0.2 percent.

If the new projections prove accurate, they would mark the worst annual showing since an 11 percent plunge in 1946.

"The slide in our economy is very severe and very broad across all industries and regions of the country," said Mark Zandi, chief economist at Moody's Economy.com. "It is about as dark an economic time that we've experienced since the 1930s."

Before yesterday's report was released, many economists were projecting an annualized drop of 5 percent in the current January-March quarter.

Given the fourth quarter's showing and the dismal state of the jobs market, some economists think a decline of close to 6 percent in the current quarter is possible.

The nation's jobless rate is now at 7.6 percent, the highest in more than 16 years. The Federal Reserve expects that to climb to close to 9 percent this year, and probably stay elevated into 2011.

On Wall Street, stocks fell yesterday as investors reacted to a decision by Citigroup Inc. to turn over a big piece of itself to the government and a move by General Electric Co. to slash its quarterly dividend by 68 percent. Investors also paid close attention to the lower GDP figures.

The faster downhill slide in the final quarter of 2008 came as the financial crisis — the worst since the 1930s — intensified. Both the new and the old fourth-quarter figures marked the weakest quarterly showing since an annualized drop of 6.4 percent in the first quarter of 1982, when the country was suffering through an intense recession.

For all of 2008, the economy grew just 1.1 percent. That was down from a 2 percent gain in 2007 and marked the slowest growth since the last recession, in 2001.

In the fourth quarter, consumers cut spending at a 4.3 percent pace. That was deeper than the initial 3.5 percent annualized drop and marked the biggest decline since the second quarter of 1980.

Businesses slashed spending on equipment and software at an annualized pace of 28.8 percent in the final quarter of last year. That was deeper than first reported and the worst showing since the first quarter of 1958.

Fallout from the housing collapse spread to other areas. Builders cut spending on commercial construction projects 21.1 percent, the most since the first quarter of 1975. Home builders slashed spending at a 22.2 percent pace.

In the long run, the reduction in new projects should aid the housing market's recovery as fewer properties for sale help increase competition and stabilize prices. But at the moment, a stable housing market appears months away.

A sharper drop in U.S. exports also factored into the weaker fourth-quarter performance. Economic troubles overseas are sapping demand for domestic goods and services.