From Pew:

The Northeast and Midwest were home to all but two of the 15 states with the slowest population growth. For a half-century, people have gravitated away from these regions and toward Sun Belt states because of employment opportunities, lower costs of living, and warmer climates.

Illinois and West Virginia were the only states with fewer residents in 2018 than a decade earlier. West Virginia lost about 34,500 people since 2008, or the equivalent of 0.19 percent a year, and has recorded population losses for the past six years.

Illinois’ growth rate was virtually flat over the same period, shedding about 6,000 residents since 2008 and losing population for the past five years.

A shrinking or slow-growing populace can be both a cause and an effect of weakened economic prospects.

Illinois and West Virginia, along with Connecticut, Mississippi, and Rhode Island, all fall near the bottom of both population and economic growth over the past decade.

Less economic activity can limit state revenue collections.

Though a smaller population can lead to a reduction in some types of spending, it also means there are fewer residents to help cover the costs of long-standing commitments, such as debt and state employee retirement benefits.