It marked the second week that claims unexpectedly leaped. The government cautioned against reading much into the past two weeks’ figures, saying they were skewed by seasonal adjustments related to Easter.

But some economists were disheartened by the report.

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Mike Feroli, economist at JP Morgan Chase Bank, called the back-to-back increases “a clear disappointment” and “a puzzle against the backdrop of generally improving economic data.”

One theory is that hiring is being held back by productivity gains. Companies are boosting production and meeting customer demand by squeezing more work from their existing staff. That means they can get by with fewer workers.

For all of 2009, workers’ productivity grew 3.8 percent. It was the fastest pace in seven years.