CASPER, Wyo. (AP) — Economists say Wyoming experienced its largest population drop since 1989 during the second half of the recent fossil fuel downturn.

U.S. Census Bureau figures released Thursday say that by mid-2017, about 8,300 more people had moved out of Wyoming than moved in compared to the previous fiscal year.

Counties in and around the Powder River Basin lost the largest number of people. The area is rich in mineral development from coal to uranium.

About 2,500 people moved out of Campbell County, the center of Wyoming's Powder River Basin coal industry, or 5.2 percent of the county's population. Campbell is also an important region for oil and gas development.

Wyoming did, however, gain some workers outside of energy hubs. Some county populations increased in tourist regions.

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