North Dakota's biggest work force development challenge is retaining college students after they graduate, a demographic researcher told business and policy leaders Thursday.

Richard Judy, chairman of Indianapolis-based Workforce Associates, reached this conclusion after conducting an in-depth analysis of the state's work force trends. He presented his findings Thursday at the Governor's Workforce Summit.

Judy's report shows that North Dakota generally experiences a net population influx of 19- to 24-year-olds, but a steep decrease of those in their later 20s.

The reason: People move here to attend the state's colleges and universities, but then move away when they find better opportunities elsewhere.

"What we're seeing is a substantial attrition of graduates to live and work somewhere else," Judy told the crowd.

The population increase among this younger demographic is a common trend in states with public universities that are well-regarded enough to attract students from neighboring states. In North Dakota, only 62 percent of students at public universities are state residents, with 22 percent coming from Minnesota and the remaining 16 percent from elsewhere.

But because of the subsequent outmigration, the population of workers ages 24 to 44 is expected to decline by 6.1 percent by 2010, according to Judy's study. At the same time, the number of North Dakotans older than 64 is expected to increase 11.9 percent by 2010.

One reason for the outmigration could be the lack of opportunity in higher-paying areas.

A separate part of Judy's analysis shows that North Dakota workers lose ground in comparison with others as they move up the wage food chain.

For example, North Dakota workers at the 10th percentile of earnings are closer to their competitors in states like Illinois and Minnesota than those at the 90th percentile of earnings, his study found.

The results were compiled from a data set representing 800 occupations, revealing a trend that's pervasive across the entire labor market.

"We've always had this history of losing students, but I don't think we've ever had a better opporunity to turn that around," said Shane Goettle, director of the state department of commerce.

The opporunity is there because the state's tightening labor market - led by a boom in the energy sector and bolstered by strength in manufacturing and agriculture - should raise wages as employers jostle for workers.

Goettle said this trend should begin to narrow the wage gap, thus helping to stem this large outmigration.