Case studies · 2008
Societe Generale and Jerome Kerviel
A junior trader hid a huge directional bet on European equity index futures behind fake offsetting trades until the unwind cost billions.
What happened
From the back office to the Delta One desk
Jerome Kerviel joined Societe Generale in the summer of 2000, straight after a Master's degree in finance. He did not start as a trader. He started in the middle and back office, the part of the bank that confirms trades, checks paperwork and makes sure a trader's booked position matches what actually happened in the market. It was unglamorous work, but it taught him exactly how the bank's control systems were built and exactly where their blind spots sat. In 2005 Kerviel was promoted to the Delta One products desk in Paris, as a junior trader in his own right.
The Delta One desk's job was arbitrage. When two related prices in European stock-index futures drifted slightly out of line, the desk would buy the cheap side and sell the expensive side, locking in a small, low-risk profit while keeping the desk's overall market exposure close to zero. Kerviel's authorised net exposure limit was EUR 125 million, a prudent size for a book that was never supposed to carry a large one-way bet on the direction of the market.
The concealment
From late 2006, and increasingly through 2007, Kerviel began entering small fictitious trades into the bank's own systems. These trades were designed to look like genuine offsetting positions, so that his book appeared balanced and low-risk on paper, while in reality he was building large, one-way directional bets on the future direction of European equity indices. He timed the fake entries so they would be cancelled or replaced just before they needed confirmation or cash settlement, staying one step ahead of the checks that should have caught them. By the end of 2007 this hidden book had generated a concealed profit of about EUR 1.4 billion, a figure so large for a supposedly low-risk desk that Kerviel chose not to report it in full, precisely because it would have drawn attention.
Discovery
The concealment held until 18-19 January 2008, when Societe Generale's internal control staff spotted irregularities and began questioning Kerviel. Over the next day, the bank established the true scale of what he had built: notional positions of about EUR 49.9 billion (commonly rounded to EUR 50 billion) across Eurostoxx 50, DAX and FTSE 100 futures. That was roughly 400 times his authorised limit, and larger than Societe Generale's own stock-market value at the time.
The unwind
Once the position was found, the bank could not simply cancel it. A futures position is a real, binding obligation, so the only way out was to sell it in the market. Societe Generale unwound the entire EUR 49.9 billion book over three trading days, 21-23 January 2008, into equity markets that were already falling sharply. The bank later said it kept its selling to around 10% of traded volume at any time to limit further damage to prices, but even so, closing a position of that size pushed prices down further, deepening the loss. The unwind crystallised a gross loss of about EUR 6.3 billion.
On 24 January 2008, Societe Generale went public. It disclosed a net trading loss of about EUR 4.9 billion, the EUR 6.3 billion gross unwind loss less the EUR 1.4 billion of profit Kerviel had hidden in 2007, alongside a capital increase to absorb the damage. Kerviel was dismissed and the bank filed a criminal complaint against him.
Eight years in the courts
What followed took eight years to settle, and the ending reshapes how the beginning should be read. On 3 July 2008, the Commission Bancaire, then France's banking supervisor, fined Societe Generale EUR 4 million, its maximum administrative penalty at the time, for what it called serious and prolonged weaknesses in internal control. On 5 October 2010, a Paris court convicted Kerviel of breach of trust, forgery and unauthorised use of computer systems, sentencing him to five years in prison (two suspended) and ordering him to pay Societe Generale EUR 4.9 billion in civil damages. The Paris Cour d'appel upheld both the conviction and the damages on 24 October 2012. Then, on 19 March 2014, France's highest court, the Cour de cassation, definitively confirmed Kerviel's criminal conviction and prison sentence, but annulled the EUR 4.9 billion damages order, ruling that the lower courts had not properly weighed Societe Generale's own control failures when setting the amount Kerviel personally owed. The damages question went back to a new court, and on 23 September 2016 the Cour d'appel de Versailles cut what Kerviel had to pay from EUR 4.9 billion to EUR 1 million, finding that deficiencies in the bank's own risk systems had contributed materially to the loss.
What margin and clearing did, and did not, catch
There was nothing exotic about the instruments themselves. Eurostoxx 50, DAX and FTSE 100 futures are liquid, exchange-traded, centrally cleared contracts, marked to market every day, with margin posted as security against loss. Daily margin and clearing did exactly what they are designed to do in this case: every real position was correctly marked to market and margined. What margin and clearing cannot do is stop an authorised employee from building a position that is simply too large, and they cannot see a position that is deliberately hidden from the firm's own risk managers behind fake offsetting trades. The safeguard works only on the exposure it can see, and here the true exposure was invisible inside the bank until it was almost too late.
Size itself then became a second source of danger, separate from the original bet. A position of about EUR 50 billion, once discovered, could not be closed quietly. Selling into an already falling market pushed prices lower still, so the act of unwinding the position added to the loss on top of whatever the market move itself would have cost. Nor was this simply a lone wrongdoer facing a blameless institution: the courts' own findings say otherwise. The regulator's 2008 fine and the French courts' final 2016 ruling both concluded that Societe Generale's internal controls were seriously and persistently deficient through 2007, which is exactly why Kerviel's criminal conviction was fully upheld while the amount he personally owed the bank was cut by more than 99 per cent.
| Date | Event |
|---|---|
| 2005 | Kerviel is promoted to the Delta One products desk in Paris, an arbitrage desk with an authorised net exposure limit of EUR 125 million. |
| Late 2006 – 2007 | Kerviel enters fictitious offsetting trades to disguise directional futures positions that exceed his authorisation, generating a concealed profit of about EUR 1.4 billion by the end of 2007. |
| 18-19 Jan 2008 | Internal control staff detect irregularities; the bank establishes the true exposure at about EUR 49.9 billion notional, roughly 400 times the desk limit. |
| 21-23 Jan 2008 | Societe Generale unwinds the entire position over three trading days into a falling market, crystallising a gross loss of about EUR 6.3 billion. |
| 24 Jan 2008 | The bank publicly discloses a net trading loss of about EUR 4.9 billion and raises capital; Kerviel is dismissed. |
| 3 Jul 2008 | The Commission Bancaire fines Societe Generale EUR 4 million for serious, prolonged control weaknesses. |
| 5 Oct 2010 | A Paris court convicts Kerviel, sentencing him to five years (two suspended) and EUR 4.9 billion in civil damages. |
| 19 Mar 2014 | The Cour de cassation confirms the criminal conviction but annuls the EUR 4.9 billion damages order. |
| 23 Sep 2016 | The Cour d'appel de Versailles sets Kerviel's personal damages at EUR 1 million, citing the bank's own control failures. |
The mathematics
Two figures fix the scale of this case: the leverage the concealment made possible, and the arithmetic behind the reported net loss. The leverage figure comes from Kerviel's true notional position divided by his authorised desk limit, which gives the multiple by which he exceeded his mandate:
$$\text{Multiple of limit} = \frac{\text{Notional}}{\text{Desk limit}} = \frac{49.9\text{bn}}{125\text{m}} \approx 399\text{x}$$
The EUR 4.9 billion net loss the bank reported follows directly from its own disclosed components: the gross loss on the January 2008 unwind less the profit hidden in 2007.
$$\text{Net loss} = \text{Gross unwind loss} - \text{Hidden 2007 profit} = 6.3\text{bn} - 1.4\text{bn} = 4.9\text{bn}$$
notional = 49.9e9 # EUR, hidden position notional (Societe Generale "10 points", Jun 2016)
desk_limit = 125e6 # EUR, desk's authorised net exposure limit (Cour de cassation, 19 Mar 2014)
hidden_profit_2007 = 1.4e9 # EUR, concealed 2007 profit
gross_unwind_loss = 6.3e9 # EUR, gross loss on the Jan 2008 unwind
reported_net_loss = 4.9e9 # EUR, net loss reported 24 Jan 2008
multiple_of_limit = notional / desk_limit
reconciled = gross_unwind_loss - hidden_profit_2007
print(f"multiple_of_limit = {multiple_of_limit:.0f}x")
print(f"reconciled = {reconciled/1e9:.2f}bn (reported: {reported_net_loss/1e9:.1f}bn)")Output
multiple_of_limit = 399x
reconciled = 4.90bn (reported: 4.9bn)The EUR 125 million limit is a small, prudent number for a genuine low-risk arbitrage book. The gap between that limit and the actual EUR 49.9 billion position is not a rounding error or a slow drift. It is a controls failure large enough that only sustained, deliberate concealment, fake trades entered and cancelled just ahead of confirmation checks, can explain it.
Data and facts
| Quantity | Value | Source |
|---|---|---|
| Hidden notional position at discovery | ≈EUR 49.9bn (≈EUR 50bn) | Societe Generale, "10 points," Jun 2016 |
| Desk's authorised net exposure limit | EUR 125m | Cour de cassation ruling, 19 Mar 2014 |
| Reported net trading loss | ≈EUR 4.9bn | Societe Generale disclosure, 24 Jan 2008 |
| Hidden profit concealed by end-2007 | ≈EUR 1.4bn | Societe Generale, "10 points" |
| Gross loss on the Jan 2008 unwind | ≈EUR 6.3bn | Societe Generale, "10 points" |
| Instrument breakdown of the position | EUR 30bn Eurostoxx 50, EUR 18bn DAX, EUR 2bn FTSE | CNBC, 27 Jan 2008 |
| Commission Bancaire fine on the bank | EUR 4m | Al Jazeera, 4 Jul 2008 |
| Societe Generale market capitalisation, Jan 2008 (context) | ≈EUR 35.9bn | Contemporaneous press |
| Kerviel's criminal sentence | 5 years (2 suspended) | Cour de cassation ruling, 19 Mar 2014 |
| Final civil damages owed by Kerviel | EUR 1m (down from EUR 4.9bn) | Cour d'appel de Versailles, 23 Sep 2016 |
The lesson
- Clearing and daily margin protect against a counterparty failing to pay. They do not, and cannot, stop an authorised trader from building a position that is far too large, and they cannot help when that position is deliberately hidden from the firm's own risk managers through fictitious trades.
- A position that is very large relative to normal trading volumes cannot be exited quietly. Once Kerviel's book was discovered, unwinding it into an already falling market made the loss larger than the original mismatched bet alone would have cost. Size becomes a risk in itself once a position must be closed under pressure.
- Concealment, not the derivative contract, was the real failure here. Eurostoxx 50, DAX and FTSE futures are ordinary, transparent, regulated instruments. The damage came from disguising a directional bet as low-risk arbitrage using fake offsetting trades, not from any defect in the futures themselves.
- Control failure is rarely one-sided. The regulator's 2008 finding and the French courts' final 2016 ruling both concluded that Societe Generale's own internal controls were seriously deficient for a prolonged period, which is why Kerviel's criminal conviction was fully upheld while his personal financial liability was cut by more than 99% once the bank's own share of the failure was weighed.
- A EUR 125 million limit breached by a factor of around 400 is not a story of gradual drift. It points to a sustained pattern of deliberate concealment that ordinary periodic reviews failed to catch for more than a year.
Where it appears in the course
Think about it
- Kerviel's fake trades were timed to be cancelled or replaced just before they needed confirmation or cash settlement. What does this tell you about which controls actually mattered here, and which ones a determined insider could route around?
- The French courts ultimately held that Societe Generale's own control failures meant Kerviel should personally repay only EUR 1 million of the EUR 4.9 billion loss, even though his criminal conviction was fully upheld. Do you think criminal responsibility and financial liability should always move together, or can they reasonably diverge like this?
- Once the bank discovered the position, it chose to unwind all of it over three days rather than, say, holding some of it and hedging the rest more gradually. What trade-offs would the bank have been weighing in making that choice?
Sources
- Societe Generale, Group Communication Division, 10 points to better understand (Kerviel case fact sheet), June 2016. societegenerale.com
- Societe Generale, "Kerviel case," corporate newsroom summary. societegenerale.com
- Cour de cassation, Chambre criminelle, ruling of 19 March 2014, no. 12-87.416. legifrance.gouv.fr
- Bloomberg, "Societe Generale Reports EU4.9 Billion Trading Loss," 25 January 2008. bloomberg.com
- NBC News/Reuters, "Societe Generale posts $4.91 billion loss," 24 January 2008. nbcnews.com
- CNBC, "French Bank Gives Details on Rogue Trader's Methods," 27 January 2008. cnbc.com
- Al Jazeera, "SocGen fined for rogue trading loss," 4 July 2008. aljazeera.com
- CNBC, "SocGen 'rogue trader' Kerviel heading for jail," 19 March 2014. cnbc.com
- France24, "French court slashes damages owed by 'rogue trader' Kerviel to EUR1 million," 23 September 2016. france24.com
- Euronews, "French court cuts damages owed by rogue trader Jerome Kerviel," 23 September 2016. euronews.com
