As everybody knows, women born in 1966, the once-every-six-decade Year of the Fire Horse, are prone to send their husbands to an early grave. Superstitious nonsense perhaps, but millions appear to have believed it. In that inauspicious year, Japan's fertility rate, previously well above 2, suddenly plummeted to 1.58. The following year it was comfortably above 2 again.

These days, Japan’s policymakers would happily settle for Fire Horse levels. In the late-1980s, Japan suffered the so-called “1.57 Shock” when its fertility rate dipped below what had been thought of as the aberration of 1966. It has been falling more or less ever since, reaching 1.26 last year, far below the 2.1 needed to keep the population stable.