Black Monday — October 19, 1987
The S&P 500 fell 22.6% in a single day
The largest single-day percentage decline in S&P 500 history. Caused by portfolio insurance (systematic selling into a declining market) creating a feedback loop. The market fully recovered within 2 years and no recession followed.
| Date | 1M return | 1Y return | 5Y return |
|---|---|---|---|
| 1987-10-19 | +8.1% | +22.9% | +81.2% |
What history says
Editorial commentary written by ALAN analysts. Figures cited below are analyst-authored context — they are not derived from the chart above and may reflect different windows or sources.
The economy never entered recession. Earnings continued growing. An investor who sold on October 20, 1987 permanently locked in a -22% loss for no fundamental reason.
After Black Monday, exchanges implemented trading halts (circuit breakers) to prevent mechanical selling cascades. These exist today at -7%, -13%, and -20% daily declines.
An investor who held through Black Monday earned +92% over the next 5 years. An investor who sold and waited for 'clarity' missed most of that gain.
Write down, in advance, what would actually change your allocation — a fundamental deterioration, not a price move. Black Monday's lesson is that a 22% one-day drop with no recession attached punished only those whose plan could be overridden by a single session's tape.