Nakako Ishiyama sits quietly in the living room of her apartment in the old Nihonbashi quarter of Tokyo, not far from its famous stone bridge—the point from which, in Edo times, all distances in Japan were measured. The neighboudiood was once part of the city’s financial district, and Ishiyama’s flat is strolling distance from the Bank of Japan, the venerable institution that controls the amount of yen in circulation and, via the interest rate it sets，the cost of money.

Ishiyama serves green tea and autumn chestnut biscuits. She has been telling me about her investment history since around 2000~the time, not coincidentally, when the Bank of Japan first pushed interest rates down to within a hair’s breadth of zero. Largely without the knowledge of her husband, Ishiyama began investing the couple’s money，mainly in lots of around $ 50,000. And didn’t stop. Each ftmd in which she entrusted their retirement nest egg or toranoko, ‘tiger’s cub”, in Japanese- has a more elaborate name than the last. As she lists each one, she invariably adds as a suffix the words nantoka nantoka-“something or other” or "thingamajig," It is not altogether reassuring.

Shy and anxious (she refused to be photographed), 66-year-old Ishiyama does not look like someone who has played a role-however modest—in the drama that has engulfed the global financial system. Yet she and many of her peers have done exactly that. Japan’s housewives have acted as the guardians of the country’s vast household savings built up since its rise to prosperity after the devastation of war. At more than ￥ l，500，000bn (some $16，800bn)，these savings are considered the world’s biggest pool of investable wealth. Most of it is stashed in ordinary Japanese bank accounts; a surprisingly large amount is kept at home in cash, in tansu savings, named for the traditional wooden cupboards in which people store their possessions. But from the early 2000$, the housewives—often referred to collectively as ”Mrs. Watanabe”, a common Japanese surname—began to hunt for higher returns.

Many were dissatisfied with the paltry interest rates banks were offering. The 0.02 percent return on a typical fixed-term deposit was so derisory that the annual payment on even substantial lifetime savings might come to a mere few hundred yen. “If you got a puncture on ttie way to the bank, you1 d be out of pocket，scoffs Ishiyama. She, like hundreds of tiiousands of others, found more appealing returns in foreign bonds and other overseas investments. "I was walking in tiie street and I saw a poster advertising a 5 percent interest rate. I got quite giddy with the idea,” she says, “I saw TV advertisements with everyone grinning and I thought: "I suppose it should be OK. ”

It wasn’t long before the markets began to notice something was stirring. In the first half of 2003, individual Japanese investors bought 2,700bn yen of foreign bonds, easily a record. Brokers were delighted, partly because they made a killing on fees. But there was nervous chatter, too: if Japanese housewives opened the floodgates and sluiced money abroad, there could be a collapse in Japan’s enormous government bond market. Hitherto, the large sums of money trapped inside the country in savings had allowed the government to negotiate remarkably low rates of interest on the country’s massive foreign debt.

Professional traders began to study Mrs. Watanabe，s every move. She impressed them by holding her nerve whenever the yen teitqwrarily strengthened, using each occasion as an opportunity to buy more foreign assets at knockdown prices. The lines of Mrs. Watanabes outside banks and brokerages became a barometer of what might happen to the yen. While highly-paid foreign-exchange traders dithered, Mrs. Watanabe cashed in and began to acquire the reputation of an investing genius. Some professionals quietly began to do whatever Mrs. Watanabe was doing.