What caused the 1987 market crash—and what can investors still learn from it today?
Imagine beginning the day with $1 million invested in the stock market and watching roughly $220,000 of market value disappear before the closing bell.
Not over the course of a year.
Not during a months-long recession.
In a single trading day.
On October 19, 1987, a day that became known as Black Monday, the Dow Jones Industrial Average fell more than 22%—the largest single-day percentage decline in its history.
To put that into perspective, a similar percentage decline today would represent an extraordinary loss of wealth in just a matter of hours.
But perhaps the most interesting part of Black Monday isn't how far the market fell.
It's what happened next.
The crash wasn't followed by another Great Depression. The U.S. economy continued growing, the stock market eventually recovered, and investors who remained focused on their long-term plans experienced a very different outcome from those who viewed one terrifying day as a reason to permanently abandon investing.
That doesn't mean Black Monday should simply be dismissed as short-term volatility.
Quite the opposite.
The crash exposed weaknesses in the way markets operated, demonstrated how quickly computerized trading and automated selling could accelerate a decline, and ultimately contributed to changes designed to slow markets during periods of extreme volatility.
It also provided investors with a powerful lesson about human behavior.
When markets are calm, it's easy to say you're a long-term investor.
When markets are falling rapidly and seemingly everyone around you is selling, that conviction can become much harder to maintain.
Nearly four decades later, technology has changed dramatically. Markets move faster. Information travels instantly. Investors can buy or sell investments from a smart phone in seconds.
But fear still feels like fear.
And that's why Black Monday remains worth studying.
Understanding what happened in 1987 isn't about preparing for another identical crash. It's about understanding how markets can behave during periods of extreme stress—and how investors can prepare themselves to make better decisions when the next difficult period inevitably arrives.
Black Monday reminds us that some of the most important investing decisions aren't made when markets are calm—they're made when everything around us feels uncertain.
Before the Crash: A Market That Had Been Soaring
Black Monday is often remembered as a sudden, unexpected collapse. But to understand why the market was vulnerable to such a dramatic decline, it helps to understand what happened in the years leading up to it.
The early and mid-1980s had been an exciting period for investors. The U.S. economy emerged from the recessions of the early 1980s, inflation fell considerably from the levels experienced during the previous decade, and economic growth strengthened.
The stock market responded.
From August 1982 through the summer of 1987, the Dow Jones Industrial Average rose dramatically. As stock prices climbed, investor optimism grew with them. By 1987, the market had already experienced several years of substantial gains, and stocks continued climbing rapidly during the first eight months of the year.
But beneath that optimism, concerns were beginning to build.
Stock valuations had risen. Interest rates were moving higher. Investors were paying closer attention to inflation, the federal budget deficit, international trade imbalances, and movements in the U.S. dollar.
Then the momentum began to change.
After reaching a record high in August 1987, the market started declining. By October, investors were already becoming increasingly nervous.
And during the week immediately preceding Black Monday, that nervousness accelerated.
The Dow fell sharply on Wednesday, October 14. It declined again on Thursday. Then on Friday, October 16, the Dow dropped more than 4%.
Investors went into the weekend with markets already under significant pressure.
When trading resumed Monday morning, there was no single headline that suddenly explained what was about to happen. Instead, several concerns collided with an increasingly fragile market.
Selling led to more selling.
Fear led to more fear.
And technology was about to make the situation even more complicated.
One of the important lessons from the period is that strong markets can sometimes create their own form of risk. Years of rising prices can make investors increasingly confident that recent performance will continue, while encouraging them to take risks they might otherwise avoid.
That doesn't mean a strong bull market automatically leads to a crash. It means investors shouldn't allow rising markets to replace a disciplined investment strategy.
Diversification, appropriate risk, reasonable expectations, and a long-term financial plan matter when markets are rising just as much as when they're falling.
Because by the morning of October 19, 1987, investors were about to discover just how quickly market confidence could disappear.
Strong markets can build wealth, but they can also build complacency—which is why a disciplined investment strategy matters long before the next market decline begins.
When Computers Started Selling
One of the most fascinating parts of Black Monday was the role that technology played.
Today, computerized trading is a normal part of financial markets. In 1987, however, markets were adapting to a relatively new world in which computers could influence trading decisions much faster than investors and traders had experienced before.
One strategy receiving considerable attention was known as portfolio insurance.
Despite the name, portfolio insurance wasn't an insurance policy. It was an investment strategy designed to help large institutional investors limit losses when stock prices declined.
The basic idea sounded reasonable.
As the market fell, the strategy called for reducing stock-market exposure, often through selling stock-index futures. If markets continued falling, the strategy called for selling even more.
In theory, this could help protect a portfolio from a severe market decline.
But there was a problem.
What might work for one investor can behave very differently when many large investors attempt to do it at the same time.
As prices fell on Black Monday, portfolio-insurance strategies generated additional selling. That selling placed more downward pressure on prices, which could trigger still more selling.
The process began feeding on itself.
At the same time, investors and institutions that weren't using portfolio insurance could see prices collapsing around them. Fear intensified, liquidity became strained, and buyers became increasingly difficult to find at prevailing prices.
Technology hadn't created the economic concerns that existed before Black Monday. Nor was portfolio insurance the only cause of the crash. But automated trading strategies helped demonstrate something investors still need to understand today:
Markets are interconnected.
An investment strategy doesn't operate in isolation. When large numbers of investors respond to the same information—or their strategies instruct them to make similar trades simultaneously—their collective actions can amplify market movements.
We've seen versions of that lesson repeatedly since 1987.
Technology has become dramatically more sophisticated. Trading occurs faster. Algorithms play a much larger role. Information that once took hours or days to reach investors can now circle the world almost instantly.
But technology hasn't eliminated human behavior.
In some cases, it can transmit that behavior faster.
That's one reason diversification and a predetermined investment plan can be so valuable. Investors who have already decided how they will respond to volatility are less dependent on making major financial decisions in the middle of a rapidly moving market.
Black Monday demonstrated that sometimes falling prices can create more selling simply because prices are falling.
And on October 19, 1987, that feedback loop helped turn an already nervous market into a historic collapse.
Technology can change how quickly markets move, but discipline, diversification, and a long-term plan can help keep short-term market movements from dictating long-term financial decisions.
The Day the Market Fell 22%
By the time investors arrived on Monday, October 19, 1987, the stock market was already under pressure.
But few could have anticipated what was about to happen.
Selling began quickly and intensified throughout the day. As stock prices fell, computerized strategies and portfolio insurance contributed to additional selling. At the same time, investors who simply wanted out of the market added to the flood of sell orders.
The problem was that there weren't enough buyers willing to step in at the prices sellers wanted.
When there are far more sellers than buyers, prices have to fall until buyers are willing to participate. On Black Monday, that process happened with extraordinary speed.
By the closing bell, the Dow Jones Industrial Average had fallen 508 points, or approximately 22.6%, in a single day.
That remains the largest one-day percentage decline in the Dow's history.
The percentage is important because today's investors are accustomed to seeing the Dow move hundreds—or even thousands—of points. But a 22% decline is in an entirely different category.
Imagine an investor beginning the morning with a $1 million stock portfolio.
If that portfolio experienced a decline similar to the Dow that day, its value could have fallen to roughly $774,000 by the closing bell.
Nothing about the underlying businesses in that portfolio had changed by 22% in a matter of hours. Factories hadn't suddenly disappeared. Companies hadn't lost 22% of their employees, customers, buildings, or long-term earning potential.
The prices investors were willing to pay for those businesses had changed dramatically.
That's an important distinction.
Stock prices can move much faster than the underlying value of the businesses they represent—particularly when fear, forced selling, liquidity problems, and investor psychology collide.
For someone watching their life savings decline that quickly, however, the distinction between price and value probably offered little comfort.
The natural reaction would have been:
Should I sell before it gets worse?
And that's where Black Monday becomes particularly useful for today's investor.
Selling might have stopped the immediate discomfort. But it would also have created another difficult decision:
When do I get back in?
An investor who sold after a major decline would need to correctly make two decisions—when to get out and when to get back in. Waiting for the market to feel safe again could mean missing part of the recovery.
That is exactly why the next part of the Black Monday story matters so much.
The crash was historic.
But the crash wasn't the end of the story.
A 22% decline in one day tested investors in an extraordinary way—but what happened afterward may provide an even more important lesson than the crash itself.
What Happened to Investors Who Stayed Invested?
After watching the Dow fall more than 22% in a single day, it would have been understandable for investors to believe the worst was still ahead.
But something very different happened.
The recovery began almost immediately. In the two trading sessions following Black Monday, the Dow regained 288 points—about 57% of the 508 points it had lost on October 19.
That didn't mean investors were immediately back to where they started. Markets remained volatile, and the recovery took time.
But consider what happened to an investor who simply stayed invested.
Before the crash, the Dow had reached a record high of 2,722.42 on August 25, 1987. On August 24, 1989—less than two years after Black Monday—it closed at a new record of 2,734.64, surpassing its pre-crash high.
The broader S&P 500 tells a similar story. From its August 1987 high through its eventual December low, it experienced a decline of roughly one-third on a price basis, yet it had recovered to its previous high by July 1989.
And there's another important piece of the story that is easy to overlook:
Dividends.
Market indexes are frequently discussed in terms of price alone. But investors who own stocks can also receive dividends, and reinvesting those dividends can help accelerate a portfolio's recovery. Looking at the S&P 500 on a total-return basis—which assumes dividends are reinvested—the recovery from its 1987 peak occurred even sooner than the price index alone suggests.
In fact, despite experiencing one of the most frightening market crashes in American history, the S&P 500 still produced a positive total return of approximately 5.25% for the full calendar year of 1987. It then returned approximately 16.61% in 1988 and 31.69% in 1989, including reinvested dividends.
Think about that for a moment.
An investor could have lived through the largest one-day percentage decline in Dow history and still ended 1987 with a positive total return if they had been invested in the S&P 500 for the entire calendar year.
That doesn't mean every investor's portfolio experienced those exact results. Different investments, allocations, purchases, withdrawals, and timing would have produced different outcomes. But it illustrates an important distinction between experiencing a market decline and permanently losing capital.
Now consider our hypothetical investor with the $1 million portfolio.
After watching the market plunge, selling everything might have felt like the safest decision. But selling would have transformed a market decline into a realized loss and introduced an entirely new problem:
When should they invest again?
Should they wait a week?
A month?
Until the economy looks better?
Until the market reaches its old high?
The problem is that markets often begin recovering before investors feel comfortable again.
That's why trying to avoid market declines can be so difficult. You don't just have to know when to sell. You also have to know when to buy again.
The research we discussed earlier illustrates how costly that second decision can become. Over the 25-year period in its analysis, an investor who remained invested experienced a 9.55% annualized return, while missing only the 10 best market days reduced that figure to 6.06%.
Black Monday provides a remarkable real-world example of why staying invested can matter.
The investor who remained invested didn't need to predict the bottom.
They didn't need to know when the recovery would begin.
They didn't need to decide when it was finally "safe" to invest again.
They simply needed the patience—and an appropriate financial plan—to allow the recovery to happen.
One of the most powerful lessons from Black Monday is that you don't necessarily need to predict when the market will recover—you need a financial plan that gives you the ability to stay invested long enough to participate when it does.
How Black Monday Changed the Market
Black Monday wasn't just a painful day for investors. It exposed weaknesses in the financial system itself.
During the crash, enormous trading volume strained the systems used by stock, options, and futures markets. These markets didn't always operate on the same clearing and settlement schedules, creating additional pressure when money and securities needed to move between institutions. And when selling accelerated, exchanges had few tools available to temporarily slow the process.
That raised an important question:
What happens when markets begin moving so quickly that investors, institutions, and even the systems supporting them struggle to keep up?
In the aftermath of the crash, regulators studied what had happened and began making changes.
One of the most important was the development of market-wide circuit breakers.
Think of a circuit breaker in your home. When an electrical system becomes overloaded, the breaker temporarily interrupts the flow of electricity before the situation becomes more dangerous.
Market circuit breakers operate on a similar principle.
Instead of allowing an extreme decline to continue uninterrupted, trading can temporarily stop. The purpose isn't to prevent markets from falling or guarantee investors against losses. It's to provide time for information to be absorbed, orders to be processed, and market participants to evaluate what is happening rather than simply reacting to a rapidly accelerating decline.
The first coordinated U.S. market-wide circuit breakers were adopted in 1988 in response to the lessons of the 1987 crash.
The rules have evolved considerably since then.
Today, market-wide circuit breakers are based on declines in the S&P 500 from the previous day's closing price. A 7% decline can trigger the first trading halt, a 13% decline can trigger another, and a 20% decline can end trading for the remainder of the day, subject to the applicable timing rules.
Black Monday also changed how regulators and market participants thought about clearing and settlement, liquidity, derivatives, risk management, and the connections between different financial markets.
The Federal Reserve played an important role as well.
The morning after the crash, newly appointed Federal Reserve Chairman Alan Greenspan publicly affirmed the Fed's readiness to provide liquidity to support the financial and economic system. Behind the scenes, the Fed also encouraged banks to continue lending. Unlike some other major financial crises, the 1987 stock-market crash was not followed by a U.S. recession or banking crisis.
That distinction is worth remembering.
A stock-market crash and an economic collapse are not necessarily the same thing.
Markets are forward-looking and heavily influenced by expectations, liquidity, positioning, and investor psychology. Prices can sometimes move dramatically even when the underlying economy hasn't deteriorated by the same magnitude.
Black Monday ultimately made financial markets better prepared for future periods of extreme volatility.
But it didn't eliminate volatility.
It didn't eliminate market crashes.
And it certainly didn't eliminate fear.
Those are risks investors still have to prepare for themselves.
The lesson of Black Monday wasn't that regulators could prevent the next market decline—it was that markets could become more resilient while investors still needed a financial plan resilient enough to withstand periods of fear and uncertainty.
What Black Monday Can Teach Investors Today
Black Monday happened nearly four decades ago, but many of the forces behind it should sound surprisingly familiar.
Markets move faster today. Investors have instant access to financial news, trading apps, social media, algorithms, and around-the-clock commentary. What once took hours to spread across Wall Street can now reach millions of investors in seconds.
But the most important part hasn't changed.
Investor behavior.
Research conducted immediately after the 1987 crash found that there wasn't one news story or rumor that caused investors to suddenly sell. Instead, anxiety was widespread, many investors believed the market was overvalued, and investor psychology played an important role in how people reacted as prices fell.
That gives us several lessons that remain relevant today.
Volatility Is Part of Investing
A diversified investment portfolio will experience periods when its value declines.
That isn't necessarily evidence that the investment strategy has stopped working.
The real question is whether the investor has an appropriate allocation for their goals, time horizon, income needs, and ability to tolerate those declines.
Someone investing for retirement 25 years from now can generally approach volatility very differently from someone who needs portfolio withdrawals next year.
That is why investment risk shouldn't simply be measured by how much the market might fall.
It should also be measured by whether your financial plan gives you enough time and flexibility to allow your investments to recover.
Diversification Matters Most When You Need It
Black Monday also reinforces why I believe diversification should go beyond simply owning a large number of investments.
A portfolio can contain hundreds—or even thousands—of securities and still have significant overlap or concentration.
The YCharts research we reviewed illustrates this particularly well. One example compares a portfolio of 531 holdings with another containing 2,935 holdings. The larger number of holdings did not automatically result in less concentration or a smaller drawdown.
True diversification can involve spreading investments across different companies, market capitalizations, investment styles, geographic regions, asset classes, and even investment managers.
This is also why active and passive strategies don't necessarily need to be competitors.
Broad-market ETFs can provide efficient exposure to large portions of the market, while active ETFs and mutual funds can introduce different investment philosophies, security-selection approaches, or risk-management strategies.
The objective isn't to own as many investments as possible.
It's to understand why you own each one and what role it plays in the portfolio.
Have a Plan Before the Market Falls
Perhaps the most practical lesson from Black Monday is that the middle of a market crisis is a terrible time to begin deciding how much risk you're comfortable taking.
Those decisions are better made beforehand.
How much should be invested in stocks?
How much should be invested more conservatively?
Where will retirement income come from during a market decline?
When should the portfolio be rebalanced?
What would actually cause you to change your investment strategy?
Answering those questions while markets are calm can make them much easier to follow when headlines become frightening.
Don't Confuse Action With Progress
When markets fall quickly, doing something can feel safer than doing nothing.
Selling can create a sense of control.
Moving everything to cash can feel like protection.
Waiting until the market "settles down" can sound prudent.
But every one of those decisions creates another decision about when to invest again.
The YCharts analysis provides a powerful illustration. Over the 25-year period it studied, remaining invested produced a 9.55% annualized return, while missing only the 10 best days reduced the annualized return to 6.06%. Missing additional top-performing days reduced results even further.
The lesson isn't that investors should blindly hold every investment forever. Portfolios should be reviewed, rebalanced, and changed when circumstances warrant.
The lesson is that fear alone isn't an investment strategy.
Black Monday demonstrated how quickly markets can become driven by selling, liquidity problems, technology, and psychology. Federal Reserve and SEC reviews of the episode have continued to emphasize those interconnected forces rather than identifying one simple cause.
Investors can't control when the next market decline will happen.
They can control how diversified they are, how much risk they take, how much liquidity they maintain, and whether they have a plan for what they'll do when markets become uncomfortable.
Successful investing isn't about avoiding every market decline—it's about building a portfolio and financial plan designed to help you stay disciplined enough to make it through them.
Final Thoughts: The Market Recovered—Would You Have Stayed Invested?
Black Monday remains one of the most extraordinary days in the history of financial markets.
In a matter of hours, the Dow Jones Industrial Average lost more than 22% of its value. Investors watched years of gains disappear, computerized trading helped accelerate selling, liquidity became strained, and fear spread rapidly through markets around the world.
For someone living through it, there was no way to know how the story would end.
That's what makes Black Monday such a valuable lesson for investors today.
Looking backward, it's easy to see that the market eventually recovered. It's much harder to remain disciplined when you're experiencing the uncertainty in real time.
An investor who stayed invested didn't need to predict the bottom.
They didn't need to know exactly when the recovery would begin.
They didn't need to wait for the headlines to become positive again.
They needed an investment strategy and financial plan that gave them the ability to stay invested.
That doesn't mean investors should ignore risk. Quite the opposite.
Black Monday reinforces why diversification matters, why your investment allocation should reflect your time horizon, why retirement investors need adequate liquidity, and why major financial decisions are better made as part of a plan rather than in response to fear.
It also reminds us that market volatility and permanent loss are not necessarily the same thing.
Markets have experienced crashes, recessions, wars, inflation, financial crises, bubbles, pandemics, and countless periods when the future looked uncertain. Every event has been different, and there is no guarantee that future recoveries will follow the same path as previous ones.
But the responsibility of the long-term investor remains remarkably similar:
Build a thoughtful portfolio.
Diversify intentionally.
Understand the risks you're taking.
Maintain enough liquidity for your near-term needs.
And have a plan you can continue following when markets become uncomfortable.
Because the next major market decline probably won't look exactly like Black Monday.
But when it arrives, investors may once again face the same difficult question:
Do I abandon my long-term plan because of what's happening today—or was my plan built to help me through moments exactly like this?
The greatest lesson from Black Monday may not be how quickly the market fell, but how important it was for investors to have a plan that allowed them to participate in the recovery that followed.
Continue Your Wealth Planning Journey
Understanding market history can help put periods of volatility into perspective, but successful investing requires more than simply knowing what happened in the past. Your portfolio should be built around your goals, time horizon, income needs, risk tolerance, and overall financial plan.
If you'd like to continue learning, I've created several complimentary wealth planning guides that explore many of the concepts discussed in this article in greater detail.
The Guide to ETF Investing and Guide to Mutual Fund Investing explore diversification, active and passive investing, manager diversification, portfolio construction, and how different investment strategies can work together.
For those approaching or already in retirement, the Guide to Retirement Income Investing explores how portfolio structure, liquidity, and retirement income planning can help address market volatility and sequence-of-returns risk.
Click the Free Wealth Guides link at the top of this page to get started today.