By this time next year the current economic expansion, if it lasts that long, will be the nation's longest ever, in peace or war.

Will it last? A number of economists think so but expect a slower pace of growth. And they are alert for straws in the wind.

"When times are good, as they now are, a recession seems miles away," said Don Hilber, an economist at Wells Fargo & Co. "Theories about 'new paradigms' and 'an end to cycles' run rampant."

That means it is a time to monitor economic data carefully for signs of an "impending contraction," he said. Right now, most indicators suggest this is unlikely but not out of the question.

For example, weak U.S. exports have drawn attention, but without a decline in the international value of the dollar this is probably not a sign of an imminent economic downturn.

One flashing signal is the general slide in profit margins, Mr. Hilber said. Rapid debt expansion is another yellow flag.

The job market also may be cooling a bit. "The employment report for March was unambiguously weak, for the first time in many, many months," said Allen Sinai of Primark Decision Economics Inc.

The number of new jobs was far lower than expected, hours worked slipped, and average hourly earnings barely rose. The unemployment rate fell to a new low of 4.2%, but both the labor force and the demand for labor shrank, which are viewed as signs of weakness.

On the other hand, no letup is apparent in spending by U.S. consumers, the main driver of the economy. Tax refunds have been a major spur lately.

"This year's entire tax refund season has been stronger than last year's," said Ian Shepardson of High Frequency Economics in Valhalla, N.Y. "The economy is booming, which means people are enjoying higher incomes and moving into higher income tax brackets, which in turn means they "earn" bigger refunds," he said.

Moreover, hints of a slowdown in the all-important housing industry are "greatly exaggerated," Mr. Shepherdson said.

In general, he said, he thinks growth could remain strong enough to raise concerns about inflation and provoke the Federal Reserve into raising interest rates.

Others are more cautious on the outlook. "There are numerous reasons to expect the economy to slow down on its own," said Nicholas S. Perna, chief economist at Fleet Financial Group in Boston.

"Despite strong economic growth and good productivity gains, corporate profits didn't rise last year," he said, squeezing corporate cash flows and ultimately slowing capital outlays by business.

Ultimately, poor profit performance heightens the chances of a stock market downturn, he said. That would be important because "soaring stock prices have helped push consumer spending up 50% faster than incomes," he said.

Even if stock prices merely flatten instead of falling, spending would probably be affected, Mr. Perna said. "And if the stock market tumbles, wealth effect becomes negative, and consumer spending will slow dramatically."

Many observers think economic growth this year will moderate to a 2% to 3% annual rate.

However, Mr. Perna said, "if the Fed and the rest of the forecasting fraternity are fooled again this year and real economic growth is closer to 4%, then the most likely result will be higher interest rates."

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