Since 2010, IL has lost almost 643,000 people on net to other states.
Meanwhile, Pennsylvania saw modest population growth of 18,400 people over the same time.
Behind Wyoming's decline rate, which was the largest in the nation, were West Virginia, Illinois, Alaska and Hawaii.
In all, 8,300 more people left Wyoming than moved to the state over the a year ago but new births meant that the total loss of population was less than that.
Looking deeper in the numbers, the explanation for the population increase for MA appears to be largely the result of an influx of people from other countries to the Bay State.
Illinois' population fell by 33,703 people to just over 12.8 million, according to the estimates.More news: Boca Raton Bowl: Florida Atlantic University Owls vs Akron Zips
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And once again, Texas' population grew by the largest number of any state in the country, as it has for every year this decade. However, in the past year, the net number of individuals moving between Kentucky and other US states was positive, albeit small.
The estimates, published by the U.S. Census Bureau, estimated population changes between July 1, 2016 and July 1, 2017.
If trends continue, the state could find itself in a downward spiral, Harger says, though he doesn't believe IL has reached that point yet. Net worldwide migration decreased 1.8 percent between 2016 and 2017, making it the first drop since 2012-2013.
Maine's population increased by around 5,600, and Rhode Island by around 2,000.
The population figures are closely watched as a sign of what will happen when congressional maps are redrawn after the 2020 Census.
The U.S. population grew by 2.3 million to 325.7 million, a less than 1% increase in population.