They called him "Mr. Five Percent" because that is how much of the world's annual copper supply he controlled. The position was unauthorised, the signatures were forged, and the losses came to $2.6 BILLION.

Yasuo Hamanaka was born in 1950. He joined Sumitomo Corporation in 1968 and spent his entire career in copper.
Sumitomo had supplied copper to Japan's shoguns since the 17th century. By the 1980s it was a global trading house. It owned no copper mines.
In 1985, his boss Saburo Shimizu lost $60 million on a failed copper deal in the Philippines.
They didn't report it.
Hamanaka was promoted to head copper trader in 1986. He decided to trade his way out of the hole.
He kept a secret book of unauthorised trades. He destroyed documents. He falsified data. He forged his supervisors' signatures on confirmation letters.
The forgeries worked.
By 1991 Sumitomo's annual report ran a double-page spread on him. Hamanaka credited his success to "expertise in risk management."
Inside the trading world he had three nicknames. "Mr. Copper." "Hammer." "Mr. Five Percent."
The five percent was how much of the world's annual copper supply he controlled.
In 1994 he set up shell trades with a private firm called Global. Global bought copper warrants from a Zambian producer. Sumitomo bought the copper from Global. Then sold the same copper back to the Zambian producer.
A circle. The copper never moved. The justification let him build a massive futures position on the London Metal Exchange.
By autumn 1995 he held two million tonnes of copper futures. By November 24, 1995, he controlled 93% of all LME copper warrants.
Anyone short copper had to buy it from him at his price.
Then China flooded the market with new supply. Prices started to fall. The CFTC and LME began investigating price manipulation.
Sumitomo discovered the secret Merrill Lynch account on May 9, 1996. They removed him from his post.
On June 5, 1996, Hamanaka confessed.
On June 13, Sumitomo announced $1.8 billion in losses. They began unwinding the positions. Copper crashed from $2,800 to $1,800 per tonne in weeks.
By September the losses were $2.6 BILLION. He had defrauded Sumitomo's Hong Kong subsidiary alone of $770 million.
He was arrested in Tokyo on October 22, 1996.
On March 26, 1998, the Tokyo District Court sentenced him to eight years for fraud and forgery. Judge Yoshifumi Asayama read the verdict. Hamanaka stood motionless, then blinked hard and swallowed.
Sumitomo paid $150 MILLION to the CFTC and $8 million to the SIB. It later sued Merrill Lynch, JPMorgan, UBS and Credit Lyonnais for aiding the fraud. Merrill settled for $275 million. JPMorgan for $125 million. UBS for $86 million.
Hamanaka was released in July 2005, a year early.
A man who controlled five percent of the world's copper did it from a desk in Tokyo with a pen and a forged signature. Sumitomo's annual report had called it expertise in risk management. The shoguns' copper company never noticed for ten years.