Sumitomo Copper Scandal: Mr Copper's $2.6bn Loss

Key Takeaways

• Yasuo Hamanaka hid about a decade of unauthorized copper trading at Sumitomo, ending in 1996.
• He cornered the London Metal Exchange copper market and forced shorts to buy from him.
• Sumitomo disclosed roughly $2.6 billion in losses and paid a $150 million CFTC penalty.
• A Tokyo court convicted Hamanaka of fraud and forgery and jailed him for eight years.

Background

Sumitomo Corporation is one of Japan's largest trading houses, with a long history in metals. Through the 1980s and 1990s, copper trading sat inside its Non-Ferrous Metals Division, and the desk was run by Yasuo Hamanaka. He became the dominant individual in the global physical and futures copper market, trading both the metal itself and contracts on the London Metal Exchange (LME), the world's main venue for industrial-metals pricing.

Traders gave Hamanaka two nicknames. He was "Mr Copper" for his aggressive style and outsized presence, and "Mr Five Percent" because he was said to control roughly 5% of the world's copper supply, according to contemporaneous reporting by The Japan Times. For years that reputation worked in his favor. A trader that large can move prices, and other participants watched his positions for direction.

The LME is structured in a way that rewards a player with deep pockets and a long-term plan. Settlement can be made in physical metal held as warehouse warrants, and the deliverable stock at any moment is finite. A buyer who accumulates both a large futures position and most of the warranted metal can squeeze anyone who has sold contracts short and cannot find copper to deliver. That structure is the lever Hamanaka used.

From the outside, the desk looked like a profit machine. Sumitomo reported gains, Hamanaka was celebrated, and his authority inside the firm grew. What the firm did not see was that the reported success rested on positions far larger than anyone had authorized, financed in ways that were being concealed, and dependent on copper never being allowed to fall.

What Happened

The scheme ran for years in the background and then unwound in a single concentrated stretch in 1996. The acute phase began once outside scrutiny of the copper market intensified.

• Mid-1980s to mid-1990s: Hamanaka runs unauthorized copper trades and conceals mounting losses. Japanese court findings later describe roughly a decade of off-the-book activity. (Japan Times; Shipping and Commodity Academy)
• Through 1995: Sumitomo builds large, dominating positions in LME copper. The U.S. Commodity Futures Trading Commission later found that during 1995 and 1996 the firm "established and maintained large and dominating futures positions in copper metal" on the LME. (CFTC Order, May 11, 1998)
• November 24, 1995: Sumitomo controls 93% of all LME warehouse copper stocks through one brokerage house alone, and at times in the fourth quarter of 1995 it and a U.S. copper merchant together control up to 100% of LME stocks. (CFTC Order)
• Late 1995 to mid-1996: The CFTC, the U.K. Securities and Investment Board (SIB) and the LME open inquiries into the copper market and Sumitomo's trading. The CFTC later says it had been investigating "a number of issues relating to the copper market and Sumitomo's trading activity" for over seven months. (CFTC Release #3918, June 14, 1996)
• June 13, 1996: Sumitomo notifies regulators of significant unreported losses in its Non-Ferrous Metals Division and announces an initial figure of about $1.8 billion. Hamanaka is removed from the desk. (Federal Reserve, Phillips testimony; CFTC Release #3918)
• June 1996: Copper prices fall sharply as the support from Sumitomo's buying is pulled away. (CFTC; Federal Reserve testimony)
• September 1996: Sumitomo discloses that total losses are far higher than first reported, at roughly $2.6 billion. (Shipping and Commodity Academy)
• March 26, 1998: The Tokyo District Court convicts Hamanaka of fraud and forgery and sentences him to eight years in prison. (Japan Times)
• May 11, 1998: The CFTC settles its manipulation case against Sumitomo for a $150 million penalty. (CFTC Release #4144-98)

By the time the dust settled, the desk that had looked like Sumitomo's most reliable earner had produced one of the biggest single-firm trading losses recorded up to that point.

Why It Happened

Two separate failures combined here, and it helps to keep them apart. One was a market-manipulation scheme. The other was a control breakdown that let the scheme run for years.

The manipulation worked through a classic corner on a physical-delivery market. Hamanaka bought copper futures on the LME and stood for delivery as contracts matured, accumulating warehouse warrants until Sumitomo held most of the deliverable metal. By November 24, 1995, the firm owned 93% of LME warehouse stocks through a single broker, and at points it and a U.S. partner controlled up to 100% of LME stocks. Anyone who had sold copper short and could not deliver physical metal was forced to buy back from the dominant holder near expiry, at whatever price that holder set. The CFTC found this conduct "directly and predictably caused copper prices, including prices in the United States cash and futures markets, to reach artificially high levels," in violation of Sections 6(c), 6(d) and 9(a)(2) of the Commodity Exchange Act.

A corner is only profitable on paper until you try to sell. Holding most of the world's deliverable copper is the same trap that catches every cornering trader. There is no one left to sell to at the inflated price, because you are the market. The position cannot be unwound quietly, so the gains exist only as long as the squeeze continues and the metal is never dumped back into a normal market.

The second failure was concealment. Hamanaka's trades ran far beyond what Sumitomo had authorized, and he hid the losses. A Tokyo court later found that he forged the signatures of his former superiors to disguise off-the-book trading and defrauded a Sumitomo subsidiary in Hong Kong out of about $770 million, according to The Japan Times. Because the reported numbers looked like profits, no internal alarm sounded for years. The court also faulted the company for failing to supervise the desk and for poor crisis management once trouble surfaced.

The last factor was simple direction risk. The entire structure assumed copper would stay high. Once regulators began scrutinizing the market and Sumitomo could no longer keep buying, the artificial price had nothing holding it up. When prices fell, the concealed losses on the giant financed position stopped being hideable.

By the Numbers

• Market share nickname: Hamanaka was called "Mr Five Percent" for reportedly controlling about 5% of the world's copper supply. (Japan Times)
• LME warehouse control: by November 24, 1995, Sumitomo owned 93% of all LME warehouse copper stocks through one brokerage house alone, and at times it and a U.S. merchant controlled up to 100% of LME stocks. (CFTC Order, May 11, 1998)
• Initial loss: about $1.8 billion, the figure Sumitomo first announced on June 13, 1996. (Federal Reserve, Phillips testimony; CFTC Release #3918)
• Total loss: roughly $2.6 billion, disclosed in September 1996, among the largest trading losses then known. (Shipping and Commodity Academy; Japan Times)
• Hong Kong fraud: the Tokyo court found Hamanaka defrauded Sumitomo's Hong Kong subsidiary of about $770 million. (Japan Times)
• CFTC penalty: $150 million total, of which $125 million was paid immediately as a civil penalty and $25 million was placed in escrow for up to four years to fund restitution to injured parties. (CFTC Release #4144-98)
• U.K. review cost: the SIB's post-scandal review of the LME cost £750,000 and was funded by the exchange. (Risk.net)
• Prison term: eight years, on conviction for fraud and forgery on March 26, 1998. (Japan Times)

Aftermath

The legal outcomes split cleanly between the trader and the firm, and both sides matter.

For Hamanaka personally, the case was criminal. On March 26, 1998, the Tokyo District Court convicted him of fraud and forgery, finding that he had defrauded a Sumitomo subsidiary and forged his superiors' signatures to hide his trading, and sentenced him to eight years in prison, as reported by The Japan Times. Reporting on the case described charges that included breach of trust alongside the fraud and forgery findings. This was a criminal conviction of an individual, not a settlement.

For Sumitomo, the case was civil and regulatory. On May 11, 1998, the CFTC settled its action against the company for $150 million. The Commission found that Sumitomo had manipulated copper prices upward in 1995 and 1996 in violation of the Commodity Exchange Act. Sumitomo neither admitted nor denied the findings, the standard language for a settled regulatory order. Of the $150 million, $125 million was a civil penalty paid to the U.S. Treasury and $25 million was escrowed for restitution. The firm also faced private litigation in the United States from parties claiming they were harmed by the inflated prices.

The episode reshaped oversight of metals markets. U.S. and U.K. regulators had coordinated closely during the inquiry, with the CFTC working alongside the SIB, the Securities and Futures Authority and the LME itself, as Chairperson Brooksley Born described in September 1996 testimony. On January 27, 1997, the SIB published a review of the LME and recommended reforms, including better transparency of trades between members. The wider lesson for regulators was that a physical-delivery market with limited position reporting could be cornered by a single dominant participant, and that cross-border information sharing was needed to catch it.

The systemic damage, by contrast, was contained. Federal Reserve Governor Susan Phillips testified on September 18, 1996, that copper markets appeared to have stabilized, that the Fed was "not aware of any material spill-over effects to other markets," and that losses appeared limited to the Sumitomo trading company, which had met its obligations to U.S. banks. The harm fell on Sumitomo's shareholders and on the traders caught in the squeeze, not on the banking system.

Lessons for Investors

1. A corner is a liquidity trap, not an edge. Hamanaka built control of up to 100% of LME copper stocks, yet that dominance was the weakness. When you hold most of a market, there is no one to sell to at the price you created, so the paper gain can only be realised by crashing the very market you control. Treat any position you cannot exit cleanly as a risk, regardless of its marked value.

2. Hidden losses compound in the dark. The scheme survived for roughly a decade because forged paperwork made losses look like profits. Concealment does not remove a loss, it lets the loss grow unmanaged. Insist on independent confirmation of positions and results, and be suspicious of any book that only ever reports success.

3. Concentration in one person is a control failure. One trader ran a desk large enough to move the world copper price, with weak supervision above him. A single point of authority with no effective check is a structural hazard, whether it is a star trader, a star fund manager, or a star executive. Separation of duties exists precisely to stop one person from both taking risk and reporting on it.

4. The rules can change underneath a crowded trade. Regulatory scrutiny and an SIB review of the LME helped end the squeeze. Any strategy that depends on lax oversight, thin reporting, or a quirk of market structure carries the risk that authorities close the gap. Before committing to a position that only works under current rules, ask what happens when those rules tighten.

5. Being right on direction does not save a hidden, financed bet. Copper demand was real, but the position was so large, so concealed, and so dependent on prices never falling that an ordinary reversal was fatal. A defensible long-term view is worthless if the sizing, financing, and transparency around it cannot survive a normal move against you.

Frequently Asked Questions

What was the Sumitomo copper scandal in simple terms? The Sumitomo copper scandal was a 1990s trading disaster in which Sumitomo's chief copper trader, Yasuo Hamanaka, ran unauthorized trades that pushed up copper prices and hid the losses for years. When it was uncovered in 1996, Sumitomo disclosed about $2.6 billion in losses.

Why did the Sumitomo copper scandal happen? It happened because Hamanaka cornered the London Metal Exchange copper market, at one point controlling most of the deliverable metal, and concealed the resulting losses with forged paperwork. Weak supervision at Sumitomo let the unauthorized trading continue for roughly a decade before it collapsed.

How much money was lost in the Sumitomo copper scandal? Sumitomo first announced about $1.8 billion in losses on June 13, 1996, then disclosed a total of roughly $2.6 billion in September 1996, one of the largest trading losses known at the time. Sumitomo later paid a $150 million penalty to settle the CFTC's manipulation case.

Could the Sumitomo copper scandal happen again today? A corner of this scale is harder now, because exchanges and regulators monitor large and dominant positions more closely and the SIB review of the LME pushed for better transparency. The basic ingredients, a finite deliverable supply and a dominant buyer, still exist, so squeezes in physical-delivery markets remain possible.

What is the main lesson from the Sumitomo copper scandal? The main lesson is that controlling a market is a trap, not a triumph. A position too large to exit, financed quietly and hidden from oversight, can produce enormous losses the moment prices turn or the rules tighten, no matter how sound the original view looked.

Sources

1. U.S. Commodity Futures Trading Commission. Release #4144-98: CFTC Files and Settles Action Against Sumitomo Corporation For Manipulating the Copper Market in 1995-96. May 11, 1998. https://www.cftc.gov/sites/default/files/opa/enf98/opa4144-98.htm
2. U.S. Commodity Futures Trading Commission. In the Matter of Sumitomo Corporation, Order. May 11, 1998. https://www.cftc.gov/sites/default/files/ogc/oporders98/ogcfsumitomo.htm
3. Federal Reserve Board. Testimony of Governor Susan M. Phillips, Implications of Trading Losses by Sumitomo Corporation. September 18, 1996. https://www.federalreserve.gov/boarddocs/testimony/1996/19960918.htm
4. U.S. Commodity Futures Trading Commission. Testimony of Chairperson Brooksley Born before the House Banking and Financial Services Committee. September 18, 1996. https://www.cftc.gov/sites/default/files/opa/speeches/opaborn-1.htm
5. U.S. Commodity Futures Trading Commission. Statement Concerning the Copper Market, Release #3918. June 14, 1996. https://www.cftc.gov/sites/default/files/opa/press96/opacopper.htm
6. Risk.net. SIB Releases Report Into LME In Wake Of Sumitomo Scandal. January 27, 1997. https://www.risk.net/derivatives/1507863/sib-releases-report-into-lme-in-wake-of-sumitomo-scandal
7. The Japan Times. Rogue copper trader draws eight-year prison term. March 26, 1998. https://www.japantimes.co.jp/news/1998/03/26/national/rogue-copper-trader-draws-eight-year-prison-term/
8. Shipping and Commodity Academy. The Sumitomo Copper Scandal of 1996: Uncovering the Involvement of Yasuo Hamanaka. https://shippingandcommodityacademy.com/blog/the-sumitomo-copper-scandal-of-1996-uncovering-the-involvement-of-yasuo-hamanaka/

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.