3. Yasuo Hamanaka Yasuo Hamanaka, a copper trader with Japan's Sumitomo Corporation, was know as Mr Five Percent, referring to the share of the copper market he controlled. His unauthorized trades over a period of 10 years led to a $2.6 billion loss for Sumitomo. Sumitomo was also charged with forging the signatures of three Sumitomo executives on documents related to his trading activities. In 1996, Hamanaka was sentenced to 8 years in prison. He was released in 2005.