Black Monday: Dow Suffers Record One-Day Percentage Drop
The 1980s bull market had driven U.S. stocks to historic highs amid deregulation, program trading, and global interconnectedness. Concerns over trade deficits, rising interest rates, and overvaluation built tension by mid-October. On October 19, 1987, the Dow Jones Industrial Average plunged 508 points or 22.6 percent in a single session—the largest one-day percentage decline in its history. Programmed selling and panic amplified the freefall, wiping out over $500 billion in market value. Markets worldwide followed with sharp losses the next day.
Why it matters: Black Monday exposed vulnerabilities in automated trading systems, prompting circuit breakers, margin reforms, and better risk management that shaped modern financial regulation. It underscored global market interdependence without triggering a prolonged depression, serving as a benchmark for later crises like 2008.