system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is Japan's population shrinking, and is this necessarily a bad thing?

Japan seems to be on a tiny island, but has a population larger than France and Germany's combined. Isn't population decline better than overpopulation, underemployment and a possible pandemic?
gpt
The population is shrinking because Japan doesn't have a very high immigration rate, and their reproduction rate is below sustainment.

One very straightforward reason why this is bad is that Japanese infrastructure has been developed to support a certain population. As that number goes down, those resources are going to waste. Further, if the population is shrinking, each newer generation will be smaller than the one that came before, leaving less and less people to support older generations as they leave the workforce.