The 2010 Flash Crash: What Happened in 36 Minutes

On the afternoon of 6 May 2010, US stock markets suddenly plunged. Within minutes, the Dow Jones Industrial Average fell by nearly 1,000 points, around 9%, temporarily erasing close to $1 trillion in market value. Some shares traded for a penny; others briefly traded at absurdly high prices. Then, almost as quickly, prices largely recovered. The whole episode took roughly half an hour.

The "Flash Crash" exposed how fragile modern, electronic markets can be when liquidity disappears. This post-mortem explains what happened, why and what changed afterwards.

1. The Background

Markets were already nervous. The European sovereign debt crisis, centred on Greece, had investors on edge, and prices were falling during the day before the crash accelerated sharply in the afternoon.

2. What Happened

• A large sell order. According to a joint report by the SEC and CFTC, a large mutual fund group used an automated algorithm to sell a very large number of E-mini S&P 500 futures contracts, worth about $4.1 billion, targeting a share of trading volume without regard to price or time.
• High-frequency traders initially bought the contracts, then quickly resold them to one another, creating a "hot potato" effect that inflated volume without adding real demand.
• Liquidity vanished. As prices fell rapidly, many market makers and automated traders stopped trading or widened their prices dramatically.
• Stub quotes executed. With few real buyers, some orders hit placeholder quotes, so shares of major companies traded for a penny while others traded at extreme highs.
• A brief pause in futures trading helped the market reset, and prices recovered much of the loss.

3. The Aftermath

• Cancelled trades. Exchanges cancelled many trades executed at clearly erroneous prices.
• Circuit breakers. Regulators introduced single-stock circuit breakers and later the "limit up-limit down" mechanism to prevent trades outside price bands.
• End of stub quotes. Market makers were required to maintain more realistic quotes.
• Better data. Regulators pushed for more comprehensive trade data, including the Consolidated Audit Trail.
• A later prosecution. In 2015, a UK trader, Navinder Sarao, was charged in the US with spoofing that authorities said contributed to market conditions that day. He later pleaded guilty.

4. Lessons for Investors

• Liquidity can disappear suddenly. Markets that seem deep in normal times can become thin in stress.
• Order types matter. Market orders and stop-loss orders can execute at very poor prices in fast markets. Limit orders offer more control.
• Automation amplifies speed. Algorithms can accelerate both declines and recoveries.
• Structure matters. Rules such as circuit breakers shape how markets behave in extreme moments.
• Private markets have their own liquidity illusions. Periodic liquidity in funds and secondaries can also vanish when many investors want out at once. See evergreen vs. traditional funds.

For other market events, see the 2008 Volkswagen short squeeze.

Frequently Asked Questions

How much did markets fall in the Flash Crash?

The Dow fell by nearly 1,000 points, around 9%, within minutes before recovering much of the loss.

What caused the Flash Crash?

Regulators pointed to a large automated sell order in stock index futures, combined with a sudden withdrawal of liquidity and interactions between high-speed traders.

Could it happen again?

Circuit breakers and other rules reduce the risk, but sudden liquidity shortages and fast price moves can still occur.

Why did some stocks trade for a penny?

Because real buyers disappeared and orders executed against placeholder "stub" quotes far from actual value.

The Bottom Line

The Flash Crash showed that modern markets can move extraordinarily fast when liquidity disappears. Reforms have made such events less likely, but the core lesson remains: liquidity is not guaranteed, and how you place orders matters most when markets are under stress.

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This article is general information, not investment advice. Figures are approximate.