Era 03 · 1987 — 1988

Circuit Breakers

Lag

1-year reaction

Pulse cycle

4.5s

Black Monday's 22.6% single-day drop exposed the fragility of fully-electronic, program-driven markets. The NYSE responded within a year — an unusually fast turnaround, precisely because the 1987 crash did not turn into a recession.

Events in this era

Oct 19, 1987

Black Monday

On October 19, 1987, the Dow dropped 22.6 percent in one session, still the largest single-day percentage decline in its history. The S&P 500 futures contract fell even harder. Portfolio insurance, a hedging strategy that sold futures as prices declined, fed a mechanical loop with program trading and cascading stop-losses. Nobody had modeled the interaction at scale. The damage did not spill into the real economy, which is why regulators had room to act in a single year rather than five.

−22.6% in one session

Oct 1988

NYSE Circuit Breakers Adopted

In October 1988, one year after Black Monday, the NYSE and SEC jointly adopted market-wide trading halts. The original thresholds were later restructured into three tiers tied to the S&P 500. A 7 percent intraday decline triggers a 15-minute Level 1 halt. A 13 percent drop produces a second 15-minute Level 2 halt. A 20 percent decline closes the market for the remainder of the session. The framework has been refined but not replaced for 38 years.

Template still in use today

Mar 9 — 18, 2020

Circuit breakers triggered four times in a week

The COVID shutdown produced the sharpest equity crash in history. The market-wide Level 1 circuit breaker (a 7 percent intraday decline) triggered four times inside ten trading days. Each halt paused trading for fifteen minutes. It was the 1988 architecture's largest real-world test, and it worked as designed.

1988 architecture vindicated at scale

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