The United States lost jobs in May for a fifth month and the unemployment rate rose a half point to 5.5 percent, the U.S. Department of Labor reported today.

Payrolls fell by 49,000 after a 28,000-job drop in April, the Labor Department said. The increase in the jobless rate was higher than every forecast in a Bloomberg News survey, as an influx of teenagers into the work force exceeded jobs available, Bloomberg reported.

A loss of jobs is one of the criteria used by the National Bureau of Economic Research to determine when recessions begin and end. The group defines contractions as a “significant’ decrease in activity over a sustained period of time.

In addition to payrolls, changes in sales, incomes, production and gross domestic product are also considered. Payrolls shrank by 324,000 workers in the first five months of the year. In 2007, the economy generated 91,000 new jobs a month on average.

Factory payrolls fell by 26,000 after declining 49,000 in April. Economists had forecast a drop of 40,000. The decrease included a drop of 7,500 computer and electronics manufacturing jobs. Auto factories added 4,400 workers.

The protracted housing slump and resulting collapse in subprime lending were also reflected in today’s report. Builders’ payrolls fell by 34,000 after decreasing by 52,000 in April. Financial firms decreased payrolls by 1,000, after a gain of 1,000 the prior month.

Service industries, which include banks, insurance companies, restaurants and retailers, added 8,000 workers after increasing by 72,000 in April. Retail payrolls decreased by 27,100 after a drop of 38,700.

Government payrolls increased by 17,000 after a gain of 12,000, indicating that the total decline in private payrolls was 66,000.

The number of Americans receiving jobless benefits surpassed 3.1 million in May for the first time in four years, indicating employees who are being let go are having a more difficult time finding new jobs.