too much inflation at once is terrible as well, but a little bit each year keeps the system going for incentivizing investing. $20 in 1990 was worth a lot more than it is today but if you didn't invest that money it's still just $20. if you did invest it it's 40 or 50 or whatever by now. it just can't rise so suddenly that wages completely fail to keep up and suddenly everyone gets hit in the teeth with expenses they weren't ready for.
Japan