Last week, when all those foreigners bolted the country they got a nice little windfall from the ongoing crisis if they traded in all their hard-earned yen for whatever currency they'd need to get by back home. When markets opened after that nerve-wracking weekend the U.S. dollar, for instance, had lost up to ¥5 since the week before, from 82 to 77. A lot of people were dumbfounded, since such a reaction flies in the face of so-called textbook economics. Why would Japan's currency get stronger as a result of such a disaster? Wouldn't people be trying to unload their yen?
The easiest explanation for the surge was the idea of "repatriation." Japanese companies with investments overseas in other currencies quickly exchanged much of their holdings into yen in order to pay for reconstruction or, in the case of insurance companies, to pay benefits to people and businesses with damage policies. However, as most Japanese economists have pointed out since then, that alone wouldn't have explained such a pronounced increase in such a short time.
According to the Mainichi Shimbun, the Great Hanshin Earthquake of 1995 created a precedent for the yen surge. Three months after that earthquake destroyed much of Kobe, the yen was the highest against the dollar that it had ever been in history up to that point. At the time, Japan's GDP was still the envy of the world, and investors with extra cash decided to buy yen, believing that it was sounder than a lot of other investments, especially since Kobe would require lots of money to rebuild. They were basically chasing the repatriated yen. As always, Japan's exporters panicked. The Bank of Japan intervened to bring the yen down, but they were unsuccessful. It wasn't until the summer, when the United States and Europe joined in the intervention, that the yen started to drop.