The number of uninsured children in America is on the rise.

An estimated 3.9 million children were uninsured in 2017, according to new research from Georgetown University’s Center for Children and Families, up from 3.6 million in 2016. Every state saw an increase in their share of uninsured children; Washington, D.C. did not.

Two charts tell the story: For the last decade, more and more American children were getting insurance coverage. Then in 2017, that trend suddenly reversed.

First the raw numbers:

You can also see it in the uninsured rate:

It’s hard to isolate one factor that contributed to that sudden spike in uninsured children. But the Georgetown researchers noted that increases were seen in every state, which suggests there was an overall national climate that contributed to the spike.

The most likely culprits, per the report:

“All of these changes in the national political and policy realm mark a sharp reversal after many years of successful efforts to reduce the uninsured rate for children and families,” the researchers wrote.

They continued:

Declines in child coverage rates occurred in 2017 despite an improving economy and low unemployment rate, strongly suggesting that federal actions contributed to a perception that publicly funded health coverage options are no longer available or, in the case of an immigrant parent, created concern about enrolling their child in public coverage for fear of reprisal. Another contributor could be changes in state Medicaid IT systems that may have tightened verification procedures. Because the majority of uninsured children (56.8 percent) are eligible for Medicaid or CHIP but are not currently enrolled, this constellation of national trends has likely created an “unwelcome mat” effect where families are unaware of their options or deterred from seeking coverage.

Hispanic and Native American children are substantially more likely to be uninsured than white or black children. Poor children are also, unsurprisingly, more likely to be uninsured than children from wealthier families.

The other most notable feature is that most of the children who lost health coverage from 2016 to 2017 live in states that refused to expand Medicaid under Obamacare: three-fourths of the 276,000, according to the Georgetown researchers.

In fact, 3 in 10 uninsured kids in the US live in either Florida or Texas, the two biggest states that have refused to expand Medicaid expansion under Obamacare.