Black Monday 1987, -22.6% in a Single Day
What if the market fell -22.6% in a single day, with no particularly bad news? Black Monday 1987 is a crash that still has no clear answer to the question "why."
The Largest Single-Day Decline in History
On Monday, October 19, 1987, the Dow Jones Industrial Average fell 508 points, about -22.6%. This remains, to this day, the largest single-day decline in U.S. stock-market history. In a single day, about $500 billion evaporated from the Dow's market value.
The crash was not confined to the U.S. but spread worldwide—to Hong Kong, Australia, Europe, and more—within hours. The global loss is estimated at about $1.71 trillion.
"Program Trading" Amplified the Decline
What was peculiar about Black Monday was that there was no clear single piece of bad news. Instead, the leading analysis is that market structure amplified the decline.
The then-popular "portfolio insurance" was a strategy that automatically sold futures to defend against losses when stock prices fell. The problem was that with everyone using the same rule, a decline triggered automatic selling, and that selling triggered further declines—a vicious cycle. Computer-based automated trading accelerated the decline faster than human fear.
After Black Monday, the New York Stock Exchange introduced the "circuit breaker" system that briefly halts trading during a sharp drop. It's a device to keep the same chain collapse from happening again.
An Unexpectedly Quick Recovery
Black Monday's drawdown didn't last as long as the Great Depression or 2008. The U.S. market recovered about 60% of the decline in just 2 trading sessions afterward, and the Dow closed 1987 slightly up for the year.
In other words, it's an event showing that "the size of a single-day drawdown" and "the time to recover" are separate matters. Because the real economy (corporate earnings, employment) was not greatly damaged, the market quickly found its footing once sentiment calmed.
Frequently Asked Questions
Q. What would have happened if I'd sold on Black Monday?
If you'd sold in panic at that day's low, you likely would have missed the rebound that began just 2 trading sessions later. This is a representative case cited to show that panic-selling in fright at a "large single-day drawdown" often becomes the worst choice. That said, it's hindsight—remember too that at the time no one knew how far that decline would go.
Q. Is a -22% single-day crash still possible today?
With the circuit-breaker system, trading is temporarily halted before it drops that much consecutively in a day. For example, circuit breakers were triggered several times during the 2020 COVID crash. The system doesn't eliminate the drawdown itself, but it controls a chain collapse of unlimited falling in a single day to some degree.
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