Save the U.S. economy. Have a baby. Make it three.

Considerable academic research suggests social insurance programs, such as Social Security and Medicare, reduce fertility rates in advanced economies. Thanks to these government-funded safety nets, parents have less incentive to produce kids to care for them in old age.

This is not just a problem that parents should care about. America’s childless ought to care a lot about the “kid gap.” Washington should care about the nation’s fertility rate the same way it cares about the nation’s productivity and labor-force participation rates. Low fertility rates are associated with diminished economic growth. Fewer kids mean fewer tax-paying workers to support public pension programs. The Obama White House has stated that real GDP growth in the 21st century “is likely to be permanently slower … due to a decline in the growth of the working age population.” An older society, noted the late Nobel laureate economist Gary Becker, is less dynamic, creative, and entrepreneurial. Thomas Piketty argues in his best-selling Capital in the Twenty-First Century that higher fertility would reduce inequality by increasing economic growth and dispersing the wealth of the rich among more descendants. And for now, at least, bigger families would boost housing demand and near-term economic growth.

Unfortunately, increasing the birth rate is hard. You really have to incentivize it.