But even after years of growth, Chinese per capita G.D.P. is still about one-third or one-fourth the size of neighboring countries like South Korea and Japan. And yet its birthrate has converged with the rich world much more quickly and completely — which has two interrelated implications, both of them grim.

First, China will have to pay for the care of a vast elderly population without the resources available to richer societies facing the same challenge. Second, China’s future growth prospects will dim with every year of below-replacement birthrates, because low fertility creates a self-reinforcing cycle — in which a less youthful society loses dynamism and growth, which reduces economic support for would-be parents, which reduces birthrates, which reduces growth ….

But alongside that Communist guilt there is Western guilt as well, because the one-child policy was linked to a project hatched by Western technocrats, funded by Western institutions, and egged on by Western intellectuals — a classist, sexist, racist, anti-religious program that sought to defuse a “population bomb” that, we know now, would have defused itself without forced sterilization programs in India and signs in Chinese villages saying “You can beat it out! You can make it fall out! You can abort it! But you cannot give birth to it!”