Twenty-five years ago President Bill Clinton signed the Family and Medical Leave Act, which included a provision giving eligible workers 12 weeks of unpaid leave to care for a new child. Emphasis on “unpaid.”

The United States remains the only country in the developed world that does not mandate employers offer paid leave for new mothers, according to the Organization for Economic Cooperation and Development.

New mothers in Finland, for instance, are entitled to up to three years worth of paid leave. Norwegian moms get up to 91 weeks. The U.K. grants new mothers up to 39 weeks, while our neighbors in the frigid Canadian north get one year.

Once again for emphasis: American moms are entitled to zero weeks of paid leave under federal law.

At the risk of stating the obvious, having kids is a necessary condition for our biological and economic survival. The species must perpetuate itself, and at the country level, if economic growth is to continue, it behooves couples to churn out as many future employees and taxpayers as possible.

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The families doing the crucial work of keeping the economy (and the species) alive, in other words, experience reduced income at a time of tremendous cost.

Every other rich nation in the world has therefore determined that it's in their interest to help these families out in their time of need and has mandated that working parents, mothers in particular, are entitled to some paid time off.

But not the United States.

Here, mandatory paid leave policies have typically been denounced as “a new national entitlement” to be avoided, a “burden on small business operators” and a decision “best left to the employer, not the government.”

But we know what happens when you leave those decisions to employers: More than 40 percent of them don't offer it at all, according to a 2016 survey of medium-to-large companies. As a result, American women have been working later into their pregnancies and going back to work sooner after birth.

This is bad for working mothers, who need time to recover from the physical and mental trauma of childbirth. It's bad for kids, who need extra attention and care in the crucial months after birth. And it's bad for the economy: Research has shown that paid maternity leave is associated with better job performance and retention among mothers, increased family incomes, and increased economic growth.

ut having children is an expensive proposition. It costs more than $233,000 to raise the typical American child from birth to age 18, according to the Agriculture Department (and that figure doesn't include the price of a college education). That works out to around $13,000 per kid per year.

Compounding those expenses is the fact that little kids — infants and toddlers — require a lot of intensive, hands-on care. That usually means that in the early years someone has to take time off work, and the biological realities of childbirth means that person is usually the mother.

Hence, household incomes drop at precisely the same time expenses skyrocket, as the chart below from the Urban Institute underscores. The typical household income falls by 10 percent at the point of childbirth in the United States and doesn't fully recover until several months later when parents are back to work.

For households headed by single women, the drop is even more drastic: 42 percent at the time of childbirth, with decreases happening in the months prior because of pregnancy-related reductions in hours worked.