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 committee views the payroll employment measure, which is based on a large survey of employers, as the most reliable comprehensive estimate of employment," said the group's statement. "This series reached a peak in December 2007 and has declined every month since then."

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.