agriculture in modern economies, IMO. Young people just don’t want to be farmers and live in small, rural towns — they’d rather live in bigger towns and cities, where there are more job opportunities, and more young people. This is a big problem in Western Europe and elsewhere, not just Japan. In Spain and Italy, they were recently selling houses for 1 euro in these rural villages to anyone who agreed to live there for a set period of time.

Having said this, I’m sure that a low birth rate and declining national population exacerbate the problem.