City-Data.com has put together a list of the Top 10 American Cities with Greatest Declining Population. Check out the list below.
1

Nevada (-6.5%pop. 6,709)
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2

Mississippi (-6.5%pop. 5,127)
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3

Arkansas (-6.4%pop. 5,921)
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4

Texas (-6.3%pop. 8,796)
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5

Kansas (-6.0%pop. 17,753)
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6

Texas (-5.9%pop. 8,945)
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7

Arkansas (-5.8%pop. 8,187)
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8

Louisiana (-5.6%pop. 4,817)
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9

Oklahoma (-5.1%pop. 8,422)
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10