Back when he was honest, King opened a postal savings account.

The most popular postal savings account, called a teigaku, yields compound annual interest semiannually but can be withdrawn without penalty after six months.

Most Japanese put money into savings accounts, mostly postal savings.

To force a reduction of the loan program, partially financed through postal savings, then-Prime Minister Junichiro Koizumi aimed to push forward postal privatization.

Last year, savers at the state-run postal savings banks faced the choice of renewing 7 percent deposits at 1 percent or investing in mutual funds.

"Everyone overestimated the amount of money that would flow out of the postal savings," Mr. Murdock said.

Many were later abolished or privatized, though some countries offer postal savings and banking through partnerships with commercial banks.

"I feel I should withdraw all our assets from other institutions as well and put them in postal savings because it's a national institution and that makes me feel safe."

Unlike postal savings, bonds issued by the Cassa are not guaranteed by the state.

With its $3 trillion in postal savings and insurance policies, Japan Post is the biggest financial institution in the world, more than twice the size of Citigroup.