WhyItDropped

S&P 500 · October 21, 1987

Two days after Black Monday

+9.10%

single-day change vs previous close

Part of a longer stretch

The Black Monday slide

midway through · 1987-08-25 → 1987-12-04, -33.51% over the whole period

What happened that day?

  • On 21 October 1987 the S&P 500 rose 9.1% in a single day
  • Two days earlier, 19 October, was Black Monday — still the worst single day on record
  • The morning after the crash the Fed issued a short statement promising to supply whatever liquidity the system needed
  • The real danger then was not the price but the settlement. If brokers could not square what they owed each other, failures would cascade
  • By effectively guaranteeing that banks would fund them, the Fed broke that chain
  • Companies announcing buybacks added to the buying. The index low, though, came in early December

Sources

Every figure on this page is recomputed from the original daily closing prices and checked against them at build time. The account of what happened is written from the sources listed above.