Wisconsin added fewer private-sector jobs in 2015 than in any year since the recession ended, according to preliminary data released by the state's Department of Workforce Development.

The numbers from a monthly survey of employers show Wisconsin added 24,500 jobs last year. By comparison, the same set of numbers showed Wisconsin added 36,900 jobs in 2014.

University of Michigan Labor Economist Donald Grimes said that there was "clearly a weakening" in Wisconsin's economy toward the end of 2015.

"If it doesn't turn around, that's a sign that things have really slowed down significantly in Wisconsin," Grimes said.

Grimes said it will be important to watch hiring trends in the first few months of this year. Marquette University Economics Professor Abdur Chowdhury agreed. "If I see this trend continue in 2016, then that would be a source of major concern," Chowdhury said.

Other metrics are more favorable for Wisconsin. For example, the state's unemployment rate is 4.3 percent, compared to 5 percent for the U.S. as a whole.

"Collectively, the indicators point to a long-term trajectory of economic and job gains in Wisconsin," said DWD spokesman John Dipko.

Economics Professor Louis Johnston of the College of St. Benedict and St. John's University in Minnesota said a slowdown in hiring is to be expected "when you're deep into a recovery period." But Chowdhury said that if that were the case, he'd expect to see slower hiring in the U.S. economy, too.

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So far that hasn't happened. Using the same set of numbers, private-sector jobs grew at a rate of 2.2 percent in the U.S. economy, more than twice as fast as the 1 percent growth in Wisconsin.

Grimes said one of the challenges facing Wisconsin is the state's "disproportionate" reliance on manufacturing.

"If manufacturing is not growing, it's going to be hard for the Wisconsin economy to grow as rapidly as the U.S.," he said.

DWD's Dipko cautioned that the December numbers are only preliminary and could still go up. They'll be revised in March.

The numbers come from the Bureau of Labor Statistics' Current Employment Statistics survey, which is sent to about 5,500 employers each month. They show private-sector job gains of 24,500 in 2015 when looking at raw, unadjusted data. When the numbers are seasonally adjusted, they drop to 23,600, which is also the lowest total since 2009.

The final word on Wisconsin's job gains won't come until June, when BLS releases its Quarterly Census of Employment and Wages covering all of 2015. That report is far more thorough and accurate than the monthly survey, which is why economists regard it as the "gold standard" of job metrics.

The most recent QCEW report covered a 12-month period ending in June of last year. It showed that Wisconsin ranked 37th in the nation in private-sector job growth, trailing most Midwest states and the national economy as a whole.