The proportion of children in the country's population has fallen to an all-time low of 13.5 per cent. That's a demographic catastrophe that is without precedent in the developed world, writes BLAINE HARDEN Japan celebrated a national holiday, last Monday, in honour 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. According to a government report, the number of children has declined for 27 consecutive years. Japan now has fewer children who are 14 or younger than at any time since 1908. The proportion of children in the population fell to an all-time low of 13.5 percent. That number has been falling for 34 straight years and is the lowest among 31 major countries, according to the report. In the United States, children account for about 20 per cent of the population. Japan also has a surfeit of the elderly. About 22 per cent of the population is 65 or older, the highest proportion in the world. And that number is on the rise. By 2020, the elderly will outnumber children by nearly 3 to 1, the government report predicted. By 2040, they will outnumber them by nearly 4 to 1. The economic and social consequences of these trends are difficult to overstate. Japan, now the world's second-largest economy, will lose 70 per cent of its workforce by 2050 and economic growth will slow to zero, according to a report this year by the nonprofit Japan Center for Economic Research. Population shrinkage began three years ago and is gathering pace. Within 50 years, the population, now 127 million, will fall by a third, the government projects. Within a century, two-thirds of the population will be gone. In what is now being called a "super-aging' society, department and grocery stores have recorded declining sales for a decade