Market Reform Act of 1990: How the 1987 Crash Led to Circuit Breakers

The Market Reform Act of 1990 gave the Securities and Exchange Commission explicit authority to impose trading halts (circuit breakers) when the stock market moves sharply, and to coordinate rules across stock, options, and futures exchanges. The law emerged directly from the wreckage of Black Monday—October 19, 1987—when the Dow fell 22% in a single day. The Brady Commission, established after the crash, blamed a cascade of automated selling, fragmented market data, and lack of inter-market coordination. Congress responded by arming the SEC with the tools to slow or stop markets when they move too fast, preventing a repeat of the panic and feedback loops that nearly broke the financial system.

The crash of October 19, 1987: the catalyst

On Black Monday, October 19, 1987, the Dow Jones Industrial Average fell 22.6% in a single trading day—the largest single-day percentage decline in stock market history. In absolute terms, nearly $500 billion in equity value evaporated in seven hours. Panic spread globally; markets in Tokyo, London, and other centers tumbled in following days.

The crash was shocking but the mechanism was more frightening to regulators. Computer-driven portfolio insurance—a hedging strategy in which portfolios automatically sold shares when prices fell, meant to limit losses—triggered a cascade. As prices fell, portfolio insurers sold more. These sales drove prices down further, triggering more insurance sales. The feedback loop fed on itself.

Equally destabilizing was the fragmentation of the market. The stock market itself operated on the NYSE and NASDAQ. But the same stocks had options listed on the Chicago Board Options Exchange and other venues, and stock index futures traded on the Chicago Mercantile Exchange. When stocks fell, traders in options and futures pits sold aggressively. But the prices of stocks, options, and futures diverged because the venues had different information systems and circuit breakers (or none). Arbitrageurs and market makers, uncertain about fair value, stopped trading. Liquidity evaporated. The market nearly ceased to function.

By the end of the day, exchanges had exhausted their backup systems, quotation services were hours late in updating prices, and many traders could not execute trades. The margin calls alone created a credit crunch—brokerages called customers demanding cash, customers couldn’t sell (the market wasn’t functioning), and some faced forced liquidations. The Federal Reserve intervened, injecting cash into the system and persuading banks to extend credit to brokerages.

The Brady Commission report

Within weeks, the SEC and the White House convened the Presidential Task Force on Market Mechanisms, chaired by Nicholas Brady (then Treasury Secretary). The Brady Commission, as it became known, spent months analyzing trading data and interviewing market participants.

The Commission’s core finding was brutal: the market structure was fragmented and lacked safeguards. Specifically:

1. No cross-market circuit breakers: Each exchange had (or lacked) its own trading halts, but there was no coordination. When the NYSE halted trading on certain stocks, the same stocks continued trading on NASDAQ or options exchanges, creating confusion and preventing price discovery.

2. Automated selling without circuit breakers: Portfolio insurance and other algorithmic strategies sold into falling markets with no mechanism to slow the selling or pause trading to allow price recovery.

3. Margin requirements and financing risk: Brokerages and futures clearinghouses weren’t required to post adequate margin or raise capital. The credit crunch threatened the financial system’s plumbing.

4. Quotation delays: With electronic quotation systems overwhelmed, traders were trading on stale prices, creating further uncertainty.

The Commission recommended that Congress grant the SEC explicit authority to impose trading halts across all venues when the market moves sharply, and that regulators coordinate rules.

Congressional response: the Market Reform Act of 1990

Congress, concerned that a repeat of Black Monday could threaten financial stability, passed the Market Reform Act of 1990 in November of that year. The law gave the SEC four key powers:

1. Authority to impose trading halts (circuit breakers)

The SEC could now set rules requiring all exchanges to halt trading when the market moves by a certain percentage or point amount. This was unprecedented. Before, the SEC could advise or suggest; now it could order halts binding on all venues.

2. Cross-market coordination

The SEC could mandate that circuit breakers and trading halts apply simultaneously across the stock market (NYSE and NASDAQ), options exchanges, and futures markets. If the stock market halted, options and futures markets halted at the same time, preventing dislocations.

3. Margin and credit safeguards

The SEC could require brokerages and clearing organizations to maintain adequate margin and capital, reducing the risk of a credit crunch during a panic.

4. Information and quotation standards

Exchanges had to maintain quotation systems that could keep pace with trading volume, preventing the delays that had exacerbated the 1987 chaos.

Circuit breaker thresholds over time

The initial circuit breaker rules, implemented by the SEC in 1988 (before the 1990 Act, on a voluntary basis), used point-based halts: a 50-point Dow drop would halt trading for 30 minutes; a 100-point drop, for one hour; a 350-point drop would close the market for the day. These thresholds were tied to the Dow’s level at the time.

As the Dow grew and inflation adjusted nominal price levels, point-based thresholds became less meaningful. In the late 1990s and 2000s, regulators shifted to percentage-based circuit breakers: a 7% decline would trigger a 15-minute halt; 13%, a one-hour halt; 20%, a full market closure. This architecture persists today and is embedded in SEC Rule 80B.

The 1990 Act in practice: lessons from subsequent crises

The circuit breaker framework was tested in the 1998 Russian financial crisis (markets fell sharply but halts prevented a cascade) and again on August 24, 2015, when the S&P 500 opened down ~3.5%, triggering a circuit breaker halt at market open. The halt lasted 15 minutes, allowing the market to stabilize and traders to reset positions. Without it, volatility likely would have spiraled.

The circuit breakers don’t prevent crashes—they can’t and shouldn’t. But they prevent cascade failures in which selling begets selling begets total market dysfunction. By forcing a pause, they give traders time to reassess, brokerages to manage margin, and the financial system to absorb shock without seizing up.

Wider implications for regulation

The Market Reform Act of 1990 established a regulatory principle: systemic risk requires systemic solutions. No single exchange’s rules are adequate; coordination across venues is necessary. Automated trading and derivatives can amplify shocks; safeguards must be mechanical and binding, not voluntary.

The 1990 Act also marked a shift in the SEC’s posture from advisor to enforcer. After 1990, the SEC had explicit statutory authority over capital markets architecture, not merely rule-by-rule tweaking. This centralization of power was debated—critics argued it was overreach; supporters argued it was necessary to prevent the next 1987.

Subsequent crises (2008 financial crisis, 2020 COVID crash, 2024 flash crashes) have seen regulators invoke or adjust circuit breakers, margin rules, and liquidity safeguards, all building on the 1990 Act’s framework.

Criticism and debate

The Market Reform Act’s circuit breaker approach has critics. Some argue that halts merely delay panic rather than resolve underlying problems; a halt won’t help if bad news is genuine. Others contend that circuit breakers reduce liquidity during volatile periods by forcing traders to stop, when continuous two-way markets (even at wider bid-ask spreads) would better allow price discovery.

There’s also debate about the threshold levels. Are 7% and 13% the right numbers, or do they need adjustment as markets grow and sentiment shifts? Regulators have tweaked them multiple times. Some academics argue for dynamic thresholds that adjust to historical volatility.

Nevertheless, the empirical record suggests circuit breakers have prevented the worst outcomes. No crash of Black Monday’s magnitude has recurred, and every major crisis since 1990 has seen circuit breakers activate without triggering total market failure. That historical record has made the architecture durable, even if imperfect.

See also