“Most innovation does not come from some disembodied laboratory,” said Stephen S. Cohen, co-director of the Berkeley Roundtable on the International Economy at the University of California, Berkeley. “In order to innovate in what you make, you have to be pretty good at making it — and we are losing that ability.”

Mr. Cohen is a partisan. He was a co-author of the 1987 book “Manufacturing Matters,” one of the first to sound an alarm as imports began to displace domestic output. But even the National Association of Manufacturers, which is supportive of members like Whirlpool and General Electric who shift production abroad, agrees that sooner or later innovation and production must go hand in hand.

Franklin J. Vargo, the association’s vice president for international economic affairs, sounds even more concerned than Mr. Cohen. “If manufacturing production declines in the United States,” he said, “at some point we will go below critical mass and then the center of innovation will shift outside the country and that will really begin a decline in our living standards.”

As it is with global warming, the crisis is in the future. Manufacturing output is not likely to fall below critical mass, as Mr. Vargo puts it, in this generation — or perhaps for several generations. The United States is still a powerhouse in manufacturing, and the output of the nation’s factories continues to rise. The problem is that the craving for manufactured goods in this country is rising faster than output, and imports are filling the gap, particularly in crucial industries.

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Measuring this growing shortfall is imprecise. The government does not do the calculation, and outsiders must put together numbers from more than one federal database to make estimates. Mr. Zandi of Moody’s Economy.com calculates that 20.5 percent of the manufactured goods bought in America last year were imported. That was up from 11.7 percent in 1992 and 20 percent in 2004. Only once since 1992 did the penetration rate slip — by four-tenths of a percentage point in 2001, a recession year.