Washington Post—Japan celebrated a national holiday on Monday in honor of its children. But Children’s Day might just as easily have been a national day of mourning. For this is the land of disappearing children and a slow-motion demographic catastrophe that is without precedent in the developed world. The number of children has declined for 27 consecutive years, a government report said over the weekend. Japan now has fewer children who are 14 or younger than at any time since 1908.