An ageing population could hold down growth and interest rates through several channels. The most direct is through the supply of labour. An economy’s potential output depends on the number of workers and their productivity. In both Germany and Japan, the working-age population has been shrinking for more than a decade, and the rate of decline will accelerate in coming years (see chart). Britain’s potential workforce will stop growing in coming decades; America’s will grow at barely a third of the 0.9% rate that prevailed from 2000 to 2013.
Pointer from Tyler Cowen.
Along seemingly similar lines, Karl Smith writes,
It’s no accident that this phenomenon appeared in Japan first. As its population began to stagnate well before the rest of the industrialized world, investors found themselves with loads of capital, a dearth of workers, and repayment terms they could not meet.
First, think about this in the absence of inter-generational transfer schemes like Social Security.
1. If people live longer than they used to, then they either have to produce more (probably by retiring later) or consume less.
2. If birth rates decline, then you let capital depreciate faster than it would otherwise. Think of an economy where the only capital goods are houses that stay in good condition for fifty years. When birth rates are rising, you need to keep using some houses longer than fifty years, even though they no longer are in good condition. When birth rates are falling, you can take some houses out of service before fifty years, even though they still are in good condition.
This seems quite straightforward to me, and it is does not suggest that demographic changes should be highly disruptive. I am not persuaded by just-so stories about Japan. One can conjure many such stories. For example, maybe Japan slowed down because its corporatist approach to capital allocation was only effective for a decade or two.