Weld County, booming because of oil and gas exploration in the Niobrara shale formation, had the largest increase in employment in the United States between December 2012 and December 2013, the U.S. Bureau of Labor Statistics said Thursday.

Weld's employment increased 6.0 percent over the year compared with the national growth of 1.8 percent.

Within Weld, the largest employment increase occurred in construction, which gained 1,864 jobs over the year or a 25.5 percent increase.

Douglas County ranked fourth in the nation for percentage employment growth growing 5.2 percent.

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