It’s an almost immutable fact: Regardless of what country you live in, and what stage of life you might be at, having kids makes you significantly less happy compared to people who don’t have kids. It’s called the parenting happiness gap.

New research to be published in the American Journal of Sociology shows that American parents are especially miserable on this front, posting the largest gap (13%) in a group of 22 developed countries.

But the research also shows that it doesn’t have to be this way. Every other country had smaller gaps, and some, including Russia, France, Finland, Sweden, Norway, Spain, Hungary, and Portugal, actually showed happiness gains for parents.

The researchers, led by Jennifer Glass at the University of Texas, looked at what impact policies such as paid sick and vacation leave and subsidized child care have on closing that gap. It was 100%.

“As social scientists we rarely completely explain anything, but in this case we completely explain the parental happiness gap,” said Glass. In countries with the strongest family-friendly policy packages, “the parental deficit in happiness was completely eliminated, accomplished by raising parent’s happiness rather than lowering nonparents’ happiness,” the authors wrote.

It’s not just one policy, like paid parental leave, that makes the difference. It’s the magic of a package of policies spanning over a lifetime, that allow people to care for children, support them financially, and even enjoy them every once in awhile on a holiday.

The study looked at 22 European and English-speaking countries using surveys from prior to the recession, including the International Social Surveys of 2007 and 2008 and the European Social Surveys of 2006 and 2008. The group created a a three-item policy index including combined paid leave available to mothers, paid vacation and sick leave, and work flexibility, and then looked at the effect of the basket of policies, as well as the impact of each individual one, on closing the happiness gap.

They found that in countries high on the comprehensive policy index, there was no gap, or, parents were even happier than non-parents. Countries low on that index were less happy.

All policies are not created equal. Paid sick and vacation leave and subsidized child care showed the largest impact on improving the happiness of non-parents as well as parents, Glass said. This is important, because policies that spend tax money to help parents at the expense of non-parents tend to be less popular.

Studies like this present some obvious challenges. For one, people in the US are actually a weirdly happy lot overall. On a scale from 1-10, they log in around the 8-10 range. People in France rate their happiness in the middle of the scale, from 5-7. “We aren’t sure if this means the French are truly less happy than Americans, or just don’t think it is appropriate to use the extremes of any scale,” Glass wrote.

To allow for these cultural differences, the research focused on the differences between parents and non-parents in the same country. They asked: “What factors are associated with parents being less happy than nonparents, given their country’s overall average level of happiness?” The key is association (or correlation), and not causation, which is impossible to prove in studies like this.

It’s no big surprise that parents in Sweden, with its dreamy parental leave policies, are happier (compared to their non-parent peers) than parents in the US, where there is no paid leave for anything—having a baby, much less raising it. But the research helps point to which policies could help most.

Glass says it’s not that parents are unhappy. They often find parenting fulfilling, and wouldn’t have it any other way. But their stress levels tend to be high, which can overshadow any happiness to be gained from shepherding another human being through life.

And why should we even care about whether parents are happy? “Parental happiness does in fact determine our fertility rates, it does determine the types of bills we get for stress-related diseases,” Glass said. “When you have a system that is not very efficient in supporting parents, you can expect to have problems motivating people to have children and care for them.”

Conversely, she said, “People want to have more children when you make it possible for them to be effective parents and effective workers.”