For the better part of the last four years, the stock market has been unstoppable. Despite a few short-lived corrections, the mature-stock-driven Dow Jones Industrial Average (^DJI -0.34%), broad-based S&P 500 (^GSPC -1.09%), and growth-focused Nasdaq Composite (^IXIC -2.15%) have all vaulted to several record-closing highs.

Investors don't have to dig too deep to find catalysts. The artificial intelligence (AI) infrastructure build-out, record-breaking initial public offerings, and better-than-expected corporate earnings have lit a fire under Wall Street's bull market.

While history conclusively shows that stocks rise over multiple decades, past events can also provide ominous warnings about short-term directional moves in the Dow, S&P 500, and Nasdaq Composite. While these prognostications don't come with a guarantee, history has a way of foreshadowing the future on Wall Street more often than not.

We're currently witnessing a unique stock market measure do something for only the fourth time since 1997. When this set of circumstances occurs, based on what history tells us, it's a look-out-below moment for stocks.

The stock market's crudest measure of risk offers a chilling outlook for Wall Street

At any given moment, several catalysts are waiting in the wings to knock Wall Street's bull market off its pedestal. There's the Federal Reserve's rate-hiking cycle, persistently elevated inflation (which prompted the aforementioned rate-hiking cycle), and historically pricey stock valuations.

But it's something far more under the radar that should concern professional and retail investors alike: outstanding margin debt.

Margin represents the money an investor borrows from their broker, with interest, to short-sell (wager against) or purchase a security. When margin is used to buy stocks or exchange-traded funds, it acts as leverage.

The lure of using margin is that it can amplify your gains if a security moves in the desired direction. However, if a security moves opposite to what's expected, margin can rapidly magnify losses. Using margin can be extremely risky, which is what makes outstanding margin debt (reported monthly by FINRA) a crude but telling measure of investors' willingness to take risks.

Over several decades, it's expected that margin debt will climb in lockstep with the overall value of public companies. But in those rare instances when outstanding margin debt goes parabolic over a short time frame, things tend to break on Wall Street.

Total Margin Debt hits $1.5 Trillion, a new all-time high 🤯 👀 https://t.co/1IXqZGgrqs

— Barchart (@Barchart) July 20, 2026

Since 1997, outstanding margin debt has surged by at least 65% over a short period on four occasions. The previous three instances all preceded significant bear markets on Wall Street:

• March 1999 to March 2000 (12 months): According to FINRA data, outstanding margin debt held by brokerages catapulted by 80% to almost $300 billion immediately preceding the bursting of the dot-com bubble. By October 2002, the benchmark S&P 500 and tech-focused Nasdaq had plunged by 49% and 78%, respectively.
• June 2006 to July 2007 (13 months): The next parabolic move in risk-taking occurred in the lead-up to the financial crisis. Over 13 months, margin debt jumped 66% to a then-record $416 billion. By March 2009, the famed S&P 500 had lost 57% of its value.
• March 2020 to October 2021 (19 months): Several rounds of stimulus checks issued after initial COVID-19 pandemic lockdowns fueled risk-taking on Wall Street. Just three months after outstanding margin debt vaulted 95% to approximately $936 billion in October 2021, the 2022 bear market took shape. The Dow, S&P 500, and Nasdaq lost around a fifth, a quarter, and a third of their respective values over nine months.
• April 2025 to June 2026 (14 months): Thus far, the AI revolution has lifted outstanding margin debt by 77% to an all-time high of $1.502 trillion in June 2026.

The historical lesson is unmistakable: outsize risk-taking foreshadows trouble for equities.

History consistently favors long-term-minded optimists

If history rhymes once more, the short-term outlook for stocks is rather chilling. But if investors simply adjust their perspective, the entire narrative changes.

The stock market is one of the world's greatest wealth creators. Even though it doesn't rise every year, the average annual return of stocks is considerably higher than other asset classes, including bonds, commodities, and real estate.

But what's most telling about the stock market's ebbs and flows is the marked disparity between optimism and pessimism.

In late May, analysts at Bespoke Investment Group published a data set on X (formerly Twitter) that examined the variance between S&P 500 bull and bear markets since the start of the Great Depression in September 1929. The difference was night and day.

On the one hand, the average S&P 500 bear market has found its trough after 286 calendar days, or about 9.5 months. Bespoke also found that no bear market has lasted longer than 630 calendar days.

The current bull market that began on 10/12/22 is now the 9th longest in S&P 500 history, surpassing the 1,324-day bull that ended on 2/9/1966: https://t.co/4mGsS2t2ft

— Bespoke (@bespokeinvest) May 30, 2026

By comparison, the typical bull market stuck around for 1,023 calendar days, which is about 3.6 times longer than the average bear market. Additionally, just over half (14) of all bull markets over the last 97 years have lasted longer than the aforementioned lengthiest bear market.

An extensive analysis from Crestmont Research tells a similar story. Crestmont calculated the rolling 20-year total returns, including dividends, of the S&P 500 since 1900. This meant tracking the performance of the S&P’s components prior to its inception in 1923.

Crestmont's annually updated data set yielded 107 rolling 20-year periods (1900-1919, 1901-1920, and so on through 2006-2025), all of which shared a common theme: a positive average annual return.

In other words, if an investor had, hypothetically, purchased an S&P 500-tracking fund at any point from 1900 to 2006 and simply held it for 20 years, they would have generated a profit every time! Not even the direst outlooks have been able to keep long-term-minded optimists from profiting.