“So why are birth rates falling all over the world? The authors knock down the conventional hypothesis that rising monetary costs are to blame. The real costs of children, they argue, are the opportunity costs: “what a potential parent would be ready to give up to have an extra child.” The seductions of the modern world include higher paying work, longer vacations, restaurant meals, sports, video games, innumerable on-demand entertainment options, and so forth. “Once we see that costs include opportunity costs, as life becomes richer and more rewarding, children cost more,” they say. “Even if we eliminated every dimension of social inequality and unfairness between women and men, the opportunity cost of having a child would still be greater in the richer, freer, better-entertained future than it was in the past.” And as demographic history shows, fewer and fewer people are willing to pay those costs.”