In 2024, the S&P 500 gained 25.02%. The average investor sitting in an equity fund that year walked away with just 16.54%, according to DALBAR's 2026 Quantitative Analysis of Investor Behavior report, an 848 basis point shortfall and the second-widest gap of the past decade, in a year when stocks did almost everything right. That single number captures the whole tension of this topic. Risk and return are supposed to move together. In practice, most people never collect the return that matches the risk they signed up for, and the reason has less to do with the market than with what happens in your head when a chart turns red.
The Basic Trade-Off: Why Safe Money Pays Less
The relationship itself is real. Data from NYU Stern going back to 1926 puts the S&P 500's annualized return at roughly 10.4% through 2025, against about 5% to 6% for a diversified bond index and 3% to 4% for Treasury bills. That gap, known as the equity risk premium, is what the market has historically paid you for tolerating uncertainty instead of parking your money somewhere predictable. The CFA Institute currently pegs a reasonable long-run estimate at 3% to 5% a year, though it's honest about the fact that estimates vary widely depending on the period and method used; pure historical comparisons across different stretches of the past century have produced figures anywhere from roughly 5% to well into double digits.
Here's the catch you don't hear often enough: that premium isn't a guaranteed paycheck, it's more like hazard pay that gets withheld in some years and paid double in others. And right now, the pay is unusually thin. By April 2026, strategists were describing the U.S. equity risk premium as having nearly vanished, with the 10-year Treasury yield near 4.29% and the S&P 500 trading around 21 times forward earnings, compressing a cushion that has typically run 300 to 500 basis points. Treasury yields have only climbed since, sitting around 4.68% to 4.70% in early August as oil prices and geopolitical tension pushed rates higher. When the "safe" option pays close to what stocks are priced to deliver, the case for taking risk has to work harder than it did a few years ago.
Why More Risk Doesn't Automatically Buy You More Return
Notice the trade-off isn't linear. Stocks carry roughly an 18% annualized standard deviation of returns against a bond index's 6%, meaning three times the year-to-year swing for maybe double the long-run return. That ratio alone should make you pause before assuming "riskier" is a synonym for "better." It also isn't universal within asset classes. Long-term U.S. corporate bonds have historically returned around 6.3% a year with roughly 8.4% volatility, edging out long-term government bonds' 5.9% return despite lower volatility, an inversion of the pattern you'd expect. Markets don't always compensate risk cleanly; sometimes an asset is simply mispriced, or the extra "risk" you're taking is uncompensated, concentration risk rather than the kind the market rewards. Betting everything on one stock isn't a bigger version of the equity risk premium. It's a different bet entirely, one with no guaranteed payoff attached.
The Real Reason the Premium Slips Through Investors' Fingers
So why did the average investor leave 848 basis points on the table in 2024, of all years? Zoom out and the pattern holds: over the trailing 20 years, the average equity fund investor has captured something like 8.7% annualized against the S&P 500's 9.7%, roughly a one-point annual drag. Run $10,000 through both rates for two decades and you get about $53,000 at 8.7% versus $63,600 at 9.7%, a difference of over $10,000 from what looks, on paper, like a rounding error.
This is where behavioral economics earns its keep. Daniel Kahneman and Amos Tversky's prospect theory, refined through decades of follow-up research, estimates that losses feel roughly twice as painful as equivalent gains feel good, a coefficient researchers have pegged around 2.0 to 2.25, though a more recent reassessment argues the true effect is smaller and more context-dependent than the famous "twice as much" shorthand suggests. Either way, the direction is consistent, and it explains the DALBAR gap better than any spreadsheet does: you don't sell a winning position out of panic, but a losing one screams at you to act. Investors pulled a record 2.30% of assets out of equity funds in a single month during 2025's volatility, DALBAR's data shows, even in a year that ultimately closed with the investor gap narrowing to just 72 basis points, its third-smallest reading since 1985. Some analysts push back on how DALBAR calculates this figure, arguing its dollar-weighted methodology can overstate the gap in edge cases. But the broader pattern, that people who move their money around in response to fear underperform people who don't, shows up too consistently across independent studies to dismiss.
How Much Risk Should You Actually Carry
This is also where financial literacy quietly fails people. The TIAA Institute's 2026 P-Fin Index found that Americans answered only 47% of its questions correctly overall, the lowest score in the survey's ten-year history, and risk comprehension was the weakest category of all eight measured, with just 36% of risk-related questions answered correctly, a struggle spanning Gen Z and Baby Boomers alike. If you've never sat down and separated your risk tolerance (how much loss you can emotionally stomach) from your risk capacity (how much loss your timeline can actually absorb), you're not unusual. A 28-year-old investing for retirement forty years out has enormous risk capacity even on a queasy stomach, because time smooths out volatility that would sink a retiree drawing income next year. Ask yourself which one actually describes you before you copy someone else's portfolio.
None of this means chasing the highest-volatility option is the goal, and it doesn't mean hiding in cash is either, especially with T-bills paying more than they have in years. It means treating the risk-return relationship as a real trade-off you're entitled to be paid for, checking whether you're actually getting paid at today's prices, and building a plan sturdy enough that you're not the one selling into the next downturn out of instinct rather than intention.