POPULATION IMPLOSION: Desperately seeking young people.

The number of 20- to 29-year-olds in Japan has crashed from 18.3m to 12.8m since 2000, according to the World Bank. By 2040 there might be only 10.5m of them. Cities like Tama are therefore playing not a zero-sum game but a negative-sum game, frantically chasing an ever-diminishing number of young adults and children. And some of their rivals have extremely sharp elbows.

Follow the Tama river upstream, into the mountains, and you eventually reach a tiny town called Okutama. What Tama is trying to avoid has already happened there. Okutama’s population peaked in the 1950s, as construction workers flocked to the town to build a large reservoir that supplies water to Tokyo in emergencies. It has grown smaller and older ever since.

Today 47% of people in the Okutama administrative area—the town and surrounding villages—are 65 or older, and 26% are at least 75. Children have become so scarce that the large primary school is only about one-quarter full. Residents in their 70s outnumber children under ten by more than five to one.

I’ve been following Japan’s demographic decline for years, and these numbers shock even me.

The Japanese need to get back in the business of making more Japanese before there’s no Japan left.