The 2010 Flash Crash: When Algorithms Lost Control
A trillion dollars vanished in 36 minutes — then came back
"The market is a device for transferring money from the impatient to the patient."
— Warren Buffett
01A Normal Thursday Afternoon
May 6, 2010 started as an unremarkable trading day. Markets were modestly lower on concerns about the Greek debt crisis. The Dow was down about 300 points by early afternoon — notable but not alarming. Then, at 2:32 PM Eastern, something unprecedented happened. In the span of five minutes, the Dow plunged an additional 600 points. Blue-chip stocks like Procter & Gamble dropped 37%. Accenture traded at one penny per share. The entire market appeared to be in freefall.
02The 36-Minute Nightmare
At its lowest point, the Dow had fallen 998.5 points — nearly 9% — in what became the largest intraday point decline in its history at that time. Approximately $1 trillion in market value evaporated. Trading volumes exploded. Over 20,000 trades were executed at prices more than 60% away from their values just moments before. Some ETFs traded at prices that implied their underlying stocks were worthless. The market had gone haywire.
03The Cause
Investigations later revealed that a single large sell order — a $4.1 billion trade by mutual fund company Waddell & Reed — had triggered a cascade of algorithmic selling. High-frequency trading firms, which normally provide liquidity, withdrew from the market simultaneously when they detected abnormal conditions. With no buyers left, prices went into freefall. The crash exposed a fundamental vulnerability: modern markets depend on algorithmic market makers who have no obligation to stay when things get rough.
04The Recovery
Almost as quickly as it began, the crash reversed. By 3:08 PM — just 36 minutes after the plunge started — the Dow had recovered most of its losses. It closed down 348 points, a significant but manageable decline. But the damage to market confidence was lasting. Regulators subsequently implemented new circuit breakers for individual stocks and tightened rules around erroneous trades. Over 20,000 trades were canceled as "clearly erroneous."
05What It Means for Investors
The Flash Crash was a wake-up call about the fragility of modern electronic markets. It showed that liquidity is an illusion — it exists until you need it most. It demonstrated that stop-loss orders can be triggered at absurd prices during flash events. And it raised fundamental questions about whether markets controlled by algorithms serve the interests of human investors. For time-travel investors, the Flash Crash is a lesson in composure: the investors who panicked and sold at the bottom lost real money on phantom prices.
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