Teens fill out job applications as they look for jobs...

Teens fill out job applications as they look for jobs at the Southampton Youth Bureau's Job Fair at the Hampton Bays Community Center on the evening of May 18, 2010. Credit: Newsday/Thomas A. Ferrara

More Americans are moving from part-time to full-time jobs, adding to evidence of a strengthening labor market.

The number of people putting in a full week rose to 113.8 million in December, the most since February 2009, the Labor Department's monthly employment report showed. At the same time, 8.1 million people worked fewer hours because they couldn't find a full-time job, the least since January 2009.

"It's what will traditionally happen when the job market overall is beginning to improve," said Tig Gilliam, chief executive of Melville-based Adecco Group North America.

While the jobless rate over the past three months fell from 9 percent to 8.5 percent, the so-called underemployment rate, which includes part-time employees who'd prefer a full-time job, dropped by 1.2 percentage points to reach 15.2 percent. The gain in hours and earnings resulting from a full-day's work will probably help sustain consumers.

"By moving into more permanent positions, you get a more productive workforce," said Michael Gapen, a senior U.S. economist at Barclays Capital Inc. in Manhattan.

Adecco, a division of Glattbrugg, Switzerland-based Adecco SA, is the world's largest supplier of temporary workers. Gilliam said his industry "is still seeing double-digit growth in permanent placements and conversions" from part-time and temporary to full-time employment.

Payrolls increased by 200,000 workers in December and the 8.5 percent jobless rate was the lowest since February 2009, Labor Department figures showed.

"Over the last several weeks, U.S. economic data has almost universally surprised to the upside," Neil Dutta, a Bank of America economist, wrote in a Friday research report. "The employment report is a case in point."

The number of people working part-time for economic reasons fell by 1.17 million in the past three months. At the same time, average hourly earnings rose 0.2 percent to $23.24, and the average workweek increased by six minutes to 34.4 hours, according to the Labor Department.

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