The U.S. population grew last year at the slowest rate since World War I as the birth rate and immigration declined, the Census Bureau reported last week. Slowing population growth will have significant economic and social implications for the country, but especially for high-tax states.

The Census Bureau and IRS last week also released state population growth and income migration data for 2018 that show the exodus from high-tax to low-tax states is accelerating. Four states have lost population since 2010 including West Virginia (-3.3%), Illinois (-1.2%), Vermont (-0.3%) and Connecticut (-0.2%), but 10 experienced declines last year. New York was the biggest loser as a net 180,000 people left for better climes. Over the last decade New York has lost more of its population to other states (7.2%) than any other save Alaska (8%), followed by Illinois (6.8%), Connecticut (5.6%) and New Jersey (5.5%).

Hmmm, what do these states have in common? Large tax burdens and politically powerful public unions. Illinois’s property tax rates are the second highest in the country after New Jersey. The state lost $5.6 billion in adjusted gross income last year to other states, about twice as much as in 2012. Notably, income outflow hasn’t increased from Michigan or Wisconsin.

Illinois’s 4.95% flat income tax is lower than many of its neighbors, but Democrats are pushing a state constitutional amendment on the November ballot for a progressive income tax. Voters should look how that’s turned out for other high-tax states.

New York’s 12.7% top marginal rate is the second highest in the U.S. In the last two years New York has lost a net $18 billion in adjusted gross income. The wealth exodus is reducing revenue and making it harder to fund programs like Medicaid. As Gov. Andrew Cuomo groused last year, “Tax the rich, tax the rich, tax the rich. We did that. God forbid the rich leave.”