The most commonly cited arbiter of recessions is the National Bureau of Economic Research, a group of academic economists that is based in Cambridge, Mass. (Mr. Lazear referred to the group at his briefing, saying it would not be clear whether there had been a recession until the bureau had made an announcement.)

The seven economists who sit on the bureau’s recession-dating committee began exchanging e-mail messages late last year about whether the economy was on the verge of a recession. But committee members said Friday that it remained too early to know.

The bureau defines a recession as a significant, protracted decline in activity that cuts across the economy, affecting measures like income, employment, retail sales and industrial production.

“Given that definition, the committee can’t possibly call a recession until it has been going on for a while,” said Christina D. Romer, an economics professor at the University of California, Berkeley. “There is no way to know if the downturn will be sufficiently long-lasting until it has lasted for a while.”

The committee did not announce the end of the last recession — which came in November 2001 — until more than a year-and a half later. Robert J. Gordon, a Northwestern University economist on the committee, said any announcement about the start of a new recession was unlikely before the last few months of 2008 at the earliest.

Recent recessions have inevitably brought inflation-adjusted income declines for most families, which would be particularly painful given what has happened over the last decade. For a variety of reasons that economists only partly understand — including technological change and global trade — many workers have received only modest raises in recent years, despite healthy economic growth.

The median household earned ,201 in 2006, down from ,244 in 1999, according to the Census Bureau. It now looks as if a full decade may pass before most Americans receive a raise.