The evidence of a downturn has been widespread for months: slower production, stagnant wages and hundreds of thousands of lost jobs. But the National Bureau of Economic Research, which is charged with making the call for the history books, waited until now to weigh in.

In a statement released Monday, the members of the group's Business Cycle Dating Committee - made up of seven prominent economists, most from the academia - said the economy entered a recession in December 2007, when economic activity peaked.