NEW YORK (CNNMoney.com) -- The National Bureau of Economic Research said Monday that the U.S. has been in a recession since December 2007, making official what most Americans have already believed about the state of the economy .

The NBER is a private group of leading economists charged with dating the start and end of economic downturns. It typically takes a long time after the start of a recession to declare its start because of the need to look at final readings of various economic measures.

The NBER said that the deterioration in the labor market throughout 2008 was one key reason why it decided to state that the recession began last year.

Employers have trimmed payrolls by 1.2 million jobs in the first 10 months of this year. On Friday, economists are predicting the government will report a loss of another 325,000 jobs for November.

The NBER also looks at real personal income, industrial production as well as wholesale and retail sales. All those measures reached a peak between November 2007 and June 2008, the NBER said.

In addition, the NBER also considers the gross domestic product, which is the reading most typically associated with a recession in the general public.

Many people erroneously believe that a recession is defined by two consecutive quarters of economic activity declining. That has yet to take place during this recession.

This downturn longer than most

The NBER did not give any reasons or causes of the recession. But it is widely accepted that the housing downturn, which started in 2006, is a primary cause of the broader economic malaise.

The fall of housing prices from peak levels reached earlier this decade cut deeply into home building and home purchases. This also caused a sharp rise in mortgage foreclosures, which in turn resulted in losses of hundreds of billions of dollars among the nation's leading banks and a tightening of credit.

The current recession is one of the longest downturns since the Great Depression of the 1930's.

The last two recessions (1990-1991 and 2001) lasted eight months each, and only two of the 10 previous post-Depression downturns lasted as long as a full year, according to the NBER.

In a statement, White House Deputy Press Secretary Tony Fratto said that even though the recession is now official, it is more important to focus on the steps being taken to fix the economy.

"The most important things we can do for the economy right now are to return the financial and credit markets to normal, and to continue to make progress in housing, and that's where we'll continue to focus," he said. "Addressing these areas will do the most right now to return the economy to growth and job creation."

President-elect Obama's transition team did not have an immediate comment on the recession announcement. But other top Democrats said this is further proof of the need for another economic stimulus package, which Obama has advocated.

"With rising costs of living, rising unemployment, record foreclosures and depleted savings, we must do more to help families make ends meet," said Senate Majority Leader Harry Reid in a statement. "With the cooperation of our Republican colleagues, we intend to send a plan to the White House as soon as possible following President-elect Obama's inauguration next month."

How long will it go?

Nonetheless, several economists said the real concern is that there is no end in sight for the downturn.

Some suggested that the best case scenario for the economy is that it would reach bottom in the second quarter of 2009. And even if that happens, that would still make this recession the longest since the Great Depression.

Rich Yamarone, director of economic research at Argus Research, said the only good news for the economy is that some of the steps already taken by the government earlier this year could start to spur growth soon. For example, he said interest rate cuts by the Federal Reserve, which started in September 2007, "should be working their magic any day now."

In February, Congress passed a $170 billion tax rebate meant to stimulate the economy. But that only boosted GDP during the second quarter.

The financial market and credit crisis worsened during this summer, prompting Congress, the Treasury Department and the Fed to pump trillions of dollars into the economy through a variety of programs, including a $700 billion bailout of banks and Wall Street firms and hundreds of billions of lending by the Fed to major companies and lenders.

But Lakshman Achuthan, managing director of Economic Cycle Research Institute, said that at this point, the only solution for the recession is time.

"All the hand waving and real cash that policymakers are throwing at the problem won't change the fact we're stuck in this nasty recession," he said. "The ultimate cure of a recession is letting it run its course."

Achuthan's research firm tracks weekly leading economic indicators that are supposed to signal a change in direction for the economy four or five months ahead of time. Those indicators are continuing to fall at a record pace.

Still, he said he's not worried about the current recession turning into a depression, as many Americans fear.

"Even with indicators in a tailspin, this still is only a very severe recession," he said. "There's lots of gloom, but we don't see doom."