It's hard to know what drives global currency markets. Some cite economic fundamentals. Others point to the pack mentality of young currency traders. And some say "Mr. Yen" can make the difference.
Mr. Yen is the nickname of Eisuke Sakakibara, a top-ranking official in Japan's Ministry of Finance and the man in charge of foreign-exchange policy. Mr. Sakakibara is widely credited with stopping the once-invincible yen.
In April 1995, the yen hit a postwar peak of 79.75 to the dollar. The rate was crushing Japanese exporters and undermining Japan's shaky economy. Sakakibara landed the foreign-exchange job that June.
A career bureaucrat, Sakakibara was educated in economics at Tokyo University, took a Ph.D. at the University of Michigan, and later taught at Harvard University.
He is known for defending Japan's right to guide its economy on Japanese terms.
"I dislike it when Westerners come here, talk about converting us ... without understanding our basic differences," he said early in February.
Sakakibara announced deregulation measures, which increased confidence in Japan's economy, and backed the appreciation of the dollar. At the same time, central banks led by the Bank of Japan and the US Federal Reserve were buying dollars in efforts to stop the decline in its value and, later, to promote its rise. By the end of the year, the yen was trading at around 100 to the dollar.
The process was so effective - the yen has lost nearly 50 percent of its value since April 1995 - that Sakakibara lately has been trying to stop the yen from slipping.
Early last November, Mr. Yen signaled that the Finance Ministry "is not thinking of leading the yen lower ... the period of one way yen depreciation may be coming to an end."
Those words brought the yen from about 115 to the dollar to 110 or so, but the trend didn't last. The dollar turned around and now buys about 122 yen.