It`s official: The United States is in a recession -- and it started a year ago.

The nation`s economy peaked, and the recession began, in December 2007, the National Bureau of Economic Research announced today.

The group`s Business Cycle Dating Committee, the semi-official arbiter of these things, defines a recession as "a significant decline in economic activity spread across the economy, lasting more than a few months, normally visible in production, employment, real income, and other indicators."

While analysts have been all but certain that a recession has been underway for months, there has been some debate over exactly when it began. Last winter, employers started cutting jobs and growth slowed significantly, but the decline appears to have accelerated over the summer.

The committee concluded that the start of the recession was December 2007 -- due in large part, it said in a statement, to the decline in jobs that began that month. But it noted that many other data points confirm the diagnosis.

"The committee determined that the decline in economic activity in 2008 met the standard for a recession," the group said in its statement. "Evidence other than the ambiguous movements of the quarterly product-side measure of domestic production confirmed that conclusion. Many of these indicators, including monthly data on the largest component of GDP, consumption, have declined sharply in recent months."

The NBER committee could eventually conclude that the recession has already ended. However, economists outside the group think that is unlikely, given that most economic data released in recent weeks have been getting worse, not better.

The NBER is a private, nonprofit group based in Cambridge, Mass. Its Business Cycle Dating Committee currently includes seven leading macroeconomists, and they made the recession call in a conference call Friday night, according to the group`s statement.

An eighth member of the committee, Christina Romer, an economist at the University of California at Berkeley, resigned last week; she has been named chairman of the Council of Economic Advisers in the Obama administration. Her husband, fellow Berkeley economist David Romer, remained on the committee.

The Washington Post