But the bears point out that 2 percent-plus growth is sluggish growth by historical standards. During the expansion of the 2000s, for instance, annual growth rates routinely spiked above 3.5 percent, even hitting 6 percent in one quarter.

And no less of a market authority than Ben S. Bernanke, the chairman of the Federal Reserve, warns that the recent strength might not be sustained. “The recent news has been good,” he said in an interview with ABC News last month. “But I think we need to be cautious and make sure this is sustainable. And we haven’t quite yet got to the point where we can be completely confident that we’re on a track to full recovery.”

So what are the bears worried about? And what explains the last few months, in which the unemployment rate fell to 8.2 percent in March from 8.9 percent in October?

The bears point to weakness underlying current numbers. Disposable personal income, a measure of how much money Americans have left over once they have paid their taxes, has barely been increasing of late, raising questions about how much spending the debt-soaked American consumer can contribute to the recovery. The shock of growth at the end of 2011, which gave a shot in the arm to economic confidence this spring, came mostly from wholesalers restocking their inventories as well.

“Final sales are barely growing,” Professor Roubini said. “So I don’t see a sustainable recovery coming from that.”

On top of that, the bears note that some trends could be making the job gains and economic growth of the last few months seem more robust than they really are. One factor is the warm winter, which might have pulled forward economic activity from the spring. In a research note entitled “Sticking With Sluggish,” the relatively pessimistic analysts at Goldman Sachs argued that the “exceptionally mild” winter stole commerce and hiring from March and April.

Moreover, the surge of hiring in the winter, which was unexplained by growth in economic output, could have been from employers who had laid off too many workers during the recession and were swinging the other way by adding too many workers, meaning hiring might slow down again.