The Bank of Japan estimated in late August that ¥30 trillion worth of ¥10,000 bills are tucked away inside households throughout the country. This staggering amount of money may not seem much compared to the financial asset total of Japanese households, estimated at ¥1,500 trillion, but it is a serious chunk of the economy to tuck away at home.
The reasons for hoarding are both straightforward and complex. The privatization of the Japanese postal savings bank in 2007, the end of full-deposit guarantees for large accounts, and even routine computer glitches in bank records have shaken public faith in financial systems. Yet, so much uninvested and uncirculated cash kept out of investment or circulation reveals a lot about the common Japanese view of money. Of course, in Japan it is relatively safe to keep large amounts of cash around. In many other countries, cash invites crime.
Much of the cash is surely kept in hesokuri, or secret savings, a traditional custom of housewives who keep something hidden away for emergencies of all kinds. A little insurance or a "nest egg" is obviously a still-relevant concern these days, and one can imagine that large corporations and small companies have cash reserves carefully tucked someplace as well.