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• Missing just the 10 best market days over 30 years cuts your returns in half
• Missing the best 30 days drops your average annual return from 8.4% to 2.1% — below inflation
• 76% of the market’s best days occur inside bear markets or the early weeks of a new bull run
• In 2025, missing just 4 of the best days turned a solid annual gain into a loss
• Lump-sum investing beats dollar-cost averaging about two-thirds of the time historically
• The real problem: exiting requires two correct calls, not one

There’s a version of this that plays out every few months. Something breaks. A number comes in wrong, a geopolitical situation spirals, a Fed official says something the market didn’t expect. And somewhere in that fog, a reasonable-sounding voice in your head asks: what if I just waited this one out?

It feels like discipline. The data says otherwise.

The numbers on this are not subtle. Over the past 30 years, missing the S&P 500’s 10 best days cut returns in half. That alone is jarring. But here’s where it gets worse: missing the best 30 days over that same period took the average annual return from 8.4% down to 2.1% — which is actually below the average inflation rate over the same stretch. You didn’t just underperform. You lost ground in real terms, while sitting in cash feeling cautious.

The 2025 data made this even harder to ignore. According to an analysis by Ned Davis Research, Morningstar, and Hartford Funds, missing just four of the market’s best days in 2025 was enough to turn a solid annual gain into a loss. Four days. In a year. That’s the margin between staying invested and stepping aside at the wrong moment.

The part that makes this genuinely uncomfortable is where those days tend to show up. Seventy-six percent of the market’s best days have historically occurred during a bear market or within the first two months of a new bull run. Nine of the 10 single best trading days on record happened during recessions. The environment that feels most dangerous to be in is, statistically, the most costly one to miss.

The two-decision problem. Most people frame market timing as a single choice: get out now. But that’s only half of it. You also have to decide when to get back in — and that second call is typically made under worse conditions than the first. By the time clarity returns, the sharpest days of the recovery have already happened. The rebound doesn’t wait for confidence to return.

This is what makes the behavioral pull so damaging. Loss aversion is real — humans feel losses more acutely than equivalent gains, which is well-documented in behavioral finance. That wiring made sense for most of human history. In markets, it quietly works against long-term wealth. Every instinct that pushes you toward the exit during a drawdown is the same instinct that makes you hesitate on the re-entry, right when it matters most.

Slight tangent, but it matters: in 2024, the average equity fund investor underperformed the S&P 500 by 8.48%, according to DALBAR’s annual behavior study. That was the second-largest investor gap in the past decade. The index did its job. The investors didn’t — mostly because of poorly timed moves in and out.

On lump sum vs. spreading it in. For investors with cash sitting on the sidelines right now, the research is fairly consistent. Vanguard’s analysis found that lump-sum investing outperformed dollar-cost averaging about 68% of the time over the period from 1976 to 2022. A separate Vanguard study across U.S., U.K., and Australian markets showed the same pattern: lump sum wins roughly two-thirds of the time across different time periods and portfolio allocations.

The logic is straightforward. Markets trend upward more years than they trend down. Every day your capital sits uninvested is a day it isn’t compounding. The math favors getting in.

That said — dollar-cost averaging does one thing lump sum cannot. It reduces the psychological damage of a bad entry. If you invest $50,000 all at once and the market drops 10% the next week, the behavioral pressure to sell at the bottom is real and significant. DCA smooths that out. It keeps investors in the game when a rough start might otherwise push them out entirely. For investors who know themselves well enough to recognize that risk, the slightly lower expected return may be worth it.

What the evidence keeps coming back to, across decades and market regimes and different countries, is that the premium equity markets pay exists precisely because staying invested is uncomfortable. The volatility is not a bug — it’s the price of admission. Investors who get paid the most are the ones who stopped trying to choose which days to be present for and just stayed.

The market doesn’t send a warning before its best days. That’s the whole point.