Spoiler alert: Time isn't just money—in the stock market, time is the only thing that turns volatility into a friend rather than a foe.
The Core Philosophy: Two Different Mindsets
Before we look at the numbers, we have to understand that these two strategies aren't just different techniques; they are entirely different worldviews.
What is Short-Term Investing?
Short-term investing (often called trading) usually involves holding assets for anywhere from a few seconds (day trading) to a few months. The goal isn't to own a company; it's to capitalize on market sentiment, news events, or technical patterns.
What is Long-Term Investing?
Long-term investing is the art of ignoring the noise. It’s the "buy and hold" strategy where you own pieces of businesses for years or decades, betting that the global economy and corporate profits will generally increase over time.
As the SEC’s Office of Investor Education and Advocacy puts it, "Focus on long-term goals, and consider the benefits of diversification and asset allocation." They warn that short-term information found on social media often leads to emotionally-driven decisions .
The Data Showdown: Hard Numbers on Performance
Let’s get into the nitty-gritty. I’m a data guy, so I need to see the receipts. I’ve pulled historical data going back nearly a century to see how these strategies pan out.
The Case for Long-Term (The Tortoise)
If you look at the pure, unadulterated data, there is no debate about which strategy works with the highest probability of success.
According to data compiled from NYU Stern and other sources, over the last 97 years (1928–2025), the S&P 500 has delivered an average annual geometric return of approximately 10.02% including dividends .
But let's be real for a second. "Average" hides the fact that the ride is terrifying. In 2022, we saw stocks decline -18.0%. In 2008, it was much worse. However, Barbara Friedberg’s analysis of historical data points out a crucial detail: stock returns are usually higher than bond returns over time, and during each 10-year period, long-term stock market returns have been positive .
I tested this personally with a "lazy portfolio" of 60% stocks and 40% bonds. The historical data shows that this mix achieved a long-term average annual return of 8.66% , effectively tempering market swings while maintaining growth . This is the set-it-and-forget-it dream.
The Harsh Reality for Short-Term (The Hare)
Now, let’s talk about the sexy side of investing: short-term trading. It looks easy on YouTube. It is not easy in real life.
I ran a backtest using a common short-term strategy on the AInvest platform: selling stocks based on the RSI (Relative Strength Index) crossing above 70 (a signal that a stock is "overbought"). The results? From 2022 to 2025, that specific strategy on SPY returned -3.20% with a negative Sharpe ratio . Ouch.
But that’s just one strategy. The broader data is even more sobering. A landmark study published in the Journal of Financial Economics by Bessembinder, Cooper, and Zhang examined nearly 8,000 U.S. equity mutual funds from 1991 to 2020. They found that the percentage of funds that outperformed the market benchmark decreased as the investment horizon lengthened for the funds, but the takeaway for investors is clear: short-term outperformance is fleeting.
In monthly data, funds beat the SPY ETF 47.2% of the time.
Over a decade, that dropped to 38.3% .
Over the full sample horizon, only 30.3% of funds outperformed the simple S&P 500 benchmark .
Here is a table illustrating how the odds of "beating the market" collapse over time based on that study:
| Performance Metric | Success Rate vs. SPY |
|---|---|
| Monthly Returns | 47.2% |
| Annual Horizon | 41.1% |
| Decade Horizon | 38.3% |
| Full Sample Horizon | 30.3% |
Source: Advisor Perspectives / Journal of Financial Economics
Why is this? Because trading costs, fees, and bad timing eat you alive. The study noted that mutual fund investors' aggregate wealth decreased by $1.31 trillion relative to the SPY benchmark over the sample period . Trillion with a T.
Risk, Volatility, and the Sleep Test
There is a concept I call the "sleep test." If you wake up at 3 AM sweating about your portfolio, your strategy is wrong for your psychology.
Short-Term Volatility
In the short term, markets are just a voting machine—they reflect emotion. If you invest for a goal less than two years away, the general rule is that you shouldn't be in stocks at all. You should be in money market funds or cash equivalents . Why? Because if you need the money for a house down payment next year, and the market drops 20%, you don't get to "wait for it to recover." You’re just poorer.
Long-Term Compounding
Fidelity Investments highlights a crucial behavioral point: "Staying invested through downturns can seem counterintuitive but it can be key to benefiting from potential rallies." They analyzed investors during the 2008 financial crisis. Those who "stuck with it"—maintaining contributions and their asset allocation—recovered far faster than those who bailed out to cash .
I’ve felt this personally. In March 2020, watching my portfolio drop 30% in weeks was nauseating. But because I was playing the long game, I did nothing. By August, I had not only recovered but gained. My short-term trading friends were exhausted from buying and selling at exactly the wrong moments.
A Nuanced View: The Academic "Overall Tracking Performance"
You might be thinking, "Surely there is a middle ground?" There is.
Recent academic research suggests that we’ve been measuring success wrong. A 2025 study published in Applied Economics by Charteris, McCullough, and Muguto introduced a novel concept called "Overall Tracking Performance" (OTP) . They argue that traditional metrics (like tracking error) are short-term oriented and don't properly quantify long-term performance for buy-and-hold investors.
They compared ETFs using short-run metrics (tracking error) and long-run metrics (cointegration). Their finding? Rankings based on long-term metrics differ substantially from those derived from short-term metrics .
This is a game-changer. It means a fund that looks "sloppy" on a daily basis (high tracking error) might actually be very aligned with its benchmark over a 5-year cycle, and vice versa. For long-term investors, the cointegration (the long-term relationship) matters more than daily fluctuations .
Practical Application: How to Allocate Your Capital
So, how do we use this data in real life? You don't have to pick just one. I use a "bucketing" strategy, which is recommended by financial planners for women in their 30s and 40s, but it works for everyone .
The Short-Term Bucket (0-3 Years)
This is your safety money. It should be in high-yield savings accounts, Treasury bills, or money market funds. You are not here to get rich; you are here to stay not-poor. Currently, T-Bills have offered a yield around 4-5% recently, but historically, the 3-month T-Bill has averaged only about 1.93% over the long haul . It barely keeps up with inflation, but it’s safe.
The Medium-Term Bucket (3-10 Years)
This is where you might buy a diversified multi-asset portfolio. You want growth, but you can't afford a total meltdown right before you buy that vacation home. A mix of bonds and stocks works here. Historically, Baa Corporate Bonds have averaged about 6.30% .
The Long-Term Bucket (10+ Years)
This is your retirement money. This bucket should be heavy on equities. Why? Because you have the one magic ingredient that short-term traders lack: the ability to ride out downturns.
Here is a chart of historical annual returns to show you just how wild the ride is, but how resilient stocks are over time :
| Year | S&P 500 (with dividends) | Baa Corporate Bond |
|---|---|---|
| 2021 | 28.5% | 0.9% |
| 2022 | -18.0% | -15.1% |
| 2023 | 26.1% | 8.7% |
| 2024 | 24.9% | 1.74% |
| 2025 | 17.78% | 6.96% |
Source: Stern School of Business, NYU
Notice how 2022 was a disaster for everyone—both stocks and bonds fell, which is rare. But in 2023 and 2024, stocks exploded upward. If you had sold in a panic in 2022, you locked in the loss.
Conclusion: Which is Better?
If you ask "which is better?" without context, the data screams Long-Term Investing.
Short-term trading is a zero-sum game before costs, and a negative-sum game after commissions and taxes. The academic research is clear: over long horizons, the vast majority of actively traded funds underperform the simple market index . The SEC explicitly warns that "short-term investing in a volatile market carries significant risk of loss" .
However, I’m not here to tell you that short-term trading is "bad." It’s just different. It requires a skill set akin to professional poker playing—excellent risk management, emotional detachment, and a deep understanding of probabilities. Most people don't have that.
For the other 99% of us, the long-term strategy wins. It wins because it utilizes compounding. It wins because it lowers tax bills. It wins because it turns off the emotional noise of the 24-hour news cycle.
As Fidelity suggests, if you've sold out of the market and are sitting on the sidelines, the best time to reinvest is often when it feels the worst . I personally tested the "do nothing" strategy through two major crashes, and I can attest that doing nothing is often the hardest, but most rewarding, action of all.
Invest for the long term. Your future self, relaxing on a beach without a care about the daily RSI levels, will thank you.