One cause is demographics. Population growth contributes to economic growth, as in China or India today. From 1962-1984 Japan’s population grew 27%. 84-06 it grew 6.5%. On top of this the population has become increasingly elderly rather than working age. Many other factors contributed obviously, but this is a big one to explain long term growth stagnation.
It is both a difference and similarity with US today.
Our population is similarly getting older, which will eventually cause an economic burden, but immigration causes continual population growth for the US, which is a difference.
