A BARREN POLITY: The Future of the City Is Childless: America’s urban rebirth is missing something key—actual births.

Related: Birth rates hit record low for women in teens and 20s: ‘That’s a lot of empty kindergarten rooms.’

Until the 1960s, pretty much every successful society actively pressured people to have kids, and rewarded them for it. Since then, we’ve reversed the incentives. It’s not clear that this has made people happier. One of my colleagues, who has a bunch of kids, said that when he and his wife were first married they asked a lot of older couples what they liked and didn’t like after years of marriage. Nearly all of them said their biggest regret was not having more kids.

Related: The Parent Trap.