Five percent of the global population lives in the United States, but nearly a quarter of the world’s inmates are locked in American prisons. We know our incarceration rate, among the highest on the planet, is costly — and reports show the staggering number of people behind bars hasn’t significantly reduced crime

And now a new study, published Tuesday, adds another issue to the national debate over how to punish nonviolent offenders: the health and well-being of their children.

Roughly 5 million kids have — or have had — at least one incarcerated parent. In the general population, that’s 1 in every 14, according to Child Trends, a national nonprofit. The chances are much higher for black children, researchers found: 1 in 9 has had a parent in prison.

Children in poor families are three times more likely to confront this situation than kids in high-income families, the study says. The vast majority of incarcerated parents across all groups are fathers.

Of course, it's hard to definitively say how many nonviolent offenders are stuck in the criminal justice system at any given time — or that peddling heroin is truly less violent than, say, a burglary motivated by starvation.

Still, at least 331,000 adults were incarcerated in 2013 for drug offenses, or a crime that could have been as simple as carrying a pouch of marijuana, according to the Prison Policy Initiative. More than 20,000 more adults lost their freedom on immigration charges.

By the Justice Department’s calculations, for every two U.S. prisoners released, one returns to a minor child.

The report, “Parents Behind Bars: What Happens to Their Children?,” warns that kids temporarily or permanently separated from parents more often develop health problems, miss school and, eventually, break the law.

Some outcomes are intuitive: They receive less parental supervision, they tend to live in households with below-average income and they face higher rates of anxiety thanks, in part, to the emotional trauma and social stigma of losing a parent to the justice system.

Researchers don’t recommend leniency for violent offenders. But imprisoning a petty criminal could inflict outsized damage on their families, while ultimately fattening the bill for taxpayers.

“This is a significant group of kids, and their needs are great,” said David Murphey, a senior research scientist at Child Trends and co-author of the report. “The debate is too often all about the people in prison. We’d do well to shine a light on the collateral effects — the families.”

For kids with parents who are serving a sentence, Murphey recommends a couple of policies to minimize harm: Remove the barriers to communication for kids with imprisoned parents, and fund programs to create kid-friendly environments within prisons.

Last week, the Federal Communications Commission tackled one obstacle by slashing the cost of prison phone calls, which can reach $14 for a brief conversation. The new price cap for 15-minute talks is $1.65, a limit some prisons are already fighting.

Some prisons, mostly women’s prisons, have introduced special visitation programs, allowing kids to bond with their parents without enduring strict security procedures. The opportunity should be equally extended to fathers, Murphey said, so they also have the opportunity to preserve family relationships and offer emotional support to their kids.

This month, the Justice Department announced it would release 6,000 inmates early from prison, the largest one-time release of federal prisoners, in an effort to curb overcrowding and free drug offenders who received particularly harsh sentences over the last 30 years.

About two-thirds of the inmates will transition to halfway houses and home confinement before being put on supervised release. One-third are foreign citizens who will face deportation.

Officials estimate the change in sentencing guidelines could result in the relative freedom of 46,000 of the country’s estimated 100,000 drug offenders in federal prison. The action followed President Obama’s plan to grant clemency to certain drug offenders, which has so far spurred the early release of 89 prisoners.