Update, July 18, 2018: In the months after this news release was published, two states, Delaware and New Jersey, have enacted laws banning marriage, without exceptions, for all people under age 18.

A new report by UCLA Fielding School of Public Health researchers found that approximately 78,400 children in the U.S. are or have been married.

Although all states in the U.S. set 18 as the legal age minimum for marriage, exceptions to the minimum can be granted in every state under varying conditions, including parental consent and official approval.

“The United States invests public resources to prevent child marriage abroad while continuing to permit it domestically,” said the study’s lead author, Alissa Koski, a postdoctoral scholar at the Fielding School. “This inconsistency between foreign policy and domestic laws has generated surprisingly little attention.”

Researchers analyzed data collected between 2010 and 2014 from the American Community Survey, which asks about the marital status of teens ages 15 to 17.

They report that an average of 6.8 of every 1,000 girls and 5.7 of every 1,000 boys had been or were married at the time they were surveyed. Prevalence differed by state: More than 10 per 1,000 children were married in West Virginia, Hawaii and North Dakota, and fewer than four per 1,000 children were married in Maine, Rhode Island and Wyoming. The study also found that child marriages were highly unstable: Nearly a quarter of children were already separated or divorced before the age of 18.

At least 14 states have or are currently considering changes to their minimum-age-at-marriage laws that would further restrict the marriage of minors, but some of the proposed legislation has been met with strong opposition.

The study was published online by Perspectives on Sexual and Reproductive Health and will appear in the journal’s June issue.

Read the full news release.