– Eight states lost population between 2015 and 2016, and 12 others recorded their lowest population increase of the decade, as economic woes and lower birthrates hit some states harder than others.

Connecticut, Illinois, Mississippi, New York, Pennsylvania, Vermont, West Virginia and Wyoming lost population. The last time so many states registered a drop in population was from 1986 to 1987, when oil prices collapsed. Twelve Western and Southern states, along with the District of Columbia, lost population then.

Meanwhile, Alabama, California, Hawaii, Kansas, Louisiana, Maryland, Massachusetts, New Jersey, North Dakota, Oklahoma and Virginia saw anemic growth of between 0.02 and 0.66 percent in the number of people living inside their borders. That’s less than the nation’s increase in population of 0.7 percent and the lowest growth those states had experienced since 2010.

Some declines reflect national mortality and birth trends, as more deaths occur as the population ages and the millennial generation has fewer babies. That has led to the slowest population growth in the U.S. in 70 years, as Brookings Institution demographer William Frey pointed out.

Pennsylvania, for instance, had 7,677 fewer people in 2016 than it did in 2015, after having experienced growth every year since 1996. “There are more and more of us at ages where deaths are more numerous,” said Herbert Smith, director of the Population Studies Center at the University of Pennsylvania.

Like in 1986, the economies of energy-producing states such as Kansas, North Dakota, Oklahoma, West Virginia and Wyoming have suffered from low oil, natural gas and coal prices. People flee a state when jobs evaporate to find work elsewhere.

As coal production declined, West Virginia lost 9,951 people from 2015 to 2016, its fourth straight year of population loss. Wyoming lost 1,054 after having steadily gained population since 1999.

Americans are moving again in higher numbers after hunkering down during the recession. Aging baby boomers are moving to the Sun Belt or other lower-cost states to retire. Florida’s population is among the fastest-growing. Idaho, Nevada and Washington state are experiencing some of the fastest economic and job growth in the nation. And their populations grew at more than twice the national growth rate from 2015 to 2016.