The 12x Strategy: Buying Last Year's S&P 500 Winner — Does It Actually Work?

By Yogurt · 2026-09-12 · Investing Strategy

A viral backtesting experiment claims you can beat the S&P 500 by simply buying the previous year's top-performing stock every January. We ran the 20-year numbers — with and without taxes — and the results are more complicated than the headline.

At the start of every year, a simple question: what if instead of buying the S&P 500 index, you just bought whichever stock had the best year last year? No earnings calls, no analyst reports, no news-watching. Just look up the chart, find the winner, and buy it.

It sounds almost too naive to be worth testing. But a rigorous 20-year backtest tells a surprisingly compelling — and cautionary — story.

The Strategy, Explained

The rules are as simple as they get. On the first trading day of every year, identify the single stock in the S&P 500 that delivered the highest total return in the prior calendar year. Buy it. That's it. The S&P 500 index itself serves as the benchmark.

Over the past 20 years, the annual winners have included household names and surprise champions alike: Netflix dominated multiple years, followed by Nvidia, AMD, and a rotating cast of energy companies. The list is itself an education in how quickly market leadership rotates.

Scenario 1: Buy, Sell, Repeat (No Tax Shelter)

In the simplest version of the test, you invest a fixed sum, sell at year-end, and rotate into the new year's winner. You pay capital gains tax — modeled at 25% — on each winning year's gains.

Without any tax, the strategy turned an initial position into roughly $134,000 over the 20-year period, versus approximately $7,900 for the S&P 500 over the same time. The raw outperformance is staggering.

But that's a fantasy number. Add the 25% annual tax bite and the picture changes dramatically. The compound interest effect — the engine of long-term wealth — gets interrupted every December. You're resetting the clock each year, handing back a quarter of every gain to the government before you can reinvest it. The tax-adjusted returns shrink so far that the strategy barely justifies the added complexity and concentration risk.

Takeaway: If you're running this in a taxable account, the rotation version is almost certainly not worth it.

Scenario 2: Buy Every January, Never Sell ($1,000/Year for 20 Years)

The more realistic — and more interesting — version is what happens if you invest $1,000 per year in the prior year's top performer and never sell. Each year you add a fresh $1,000 to whichever stock topped the prior year's leaderboard, building a growing multi-stock portfolio.

Over 20 years, you've invested a total of $20,000.

Momentum strategy (never sell): Portfolio grew to approximately $239,000 — nearly 12x the invested capital.
S&P 500 index (same $1,000/year): Portfolio grew to roughly 4.8x the invested capital.

The outperformance is real and substantial. But the reason why it worked is where the story gets complicated.

The Three Foxes Problem

Digging into the 20 years of individual results reveals an uncomfortable truth. The strategy didn't beat the market because momentum investing is reliably superior. It beat the market almost entirely because of three extraordinary positions:

Nvidia (NVDA) — bought after its 2016 breakout year, it continued to surge as the AI narrative took hold.
AMD — bought after its 2019 run, extended its monster rally into 2020.
AMD again — the 2020 position compounded on the prior gain.

Strip those three "foxes" out of the 20-year run, and the remaining 17 annual picks collectively returned roughly the same as the S&P 500 — maybe a touch better, maybe a touch worse. The entire edge came from three bets that happened to land on two of the greatest multi-year compounders in modern market history.

If you hadn't owned those positions — if instead of AMD and NVDA your winners had been, say, an energy stock or a retailer that faded after its big year — the 20-year result would look far more ordinary.

You'll Lose to the Market More Often Than You Win

Here's the hardest part of running this strategy in real life: it only beat the S&P 500 in 12 out of 20 years. That means for eight years — nearly half the sample — you're watching your momentum pick underperform the boring index fund. Psychologically, that's brutal. In year three or four of lagging, most investors abandon the strategy — precisely before the years where a Nvidia-sized payoff might have arrived.

The emotional toll of a strategy that loses more years than it wins, in exchange for potentially massive payoffs in a minority of years, is genuinely difficult to sustain.

The Verdict: A Fun Experiment, Not a Core Strategy

The prior-year winner momentum strategy works — in aggregate, over long periods, if you never sell, and if you're lucky enough to catch one of those rare monster compounders. But it is not a set-it-and-forget-it market beater. It is a concentrated bet on continuation, and its historical edge comes almost entirely from a handful of positions that will be impossible to predict in advance.

As a small side experiment — say, $1,000 per year in a tax-advantaged account — it's an intellectually honest way to add a momentum tilt to a diversified portfolio. As your primary investment strategy, the concentration risk, the psychological difficulty of lagging for years at a time, and the outsized dependence on a few "foxes" make it a genuine gamble with your financial future.

The market will keep rotating its favorites. Whether next year's winner is another decade-defining compounder or just a flash in the pan is, as always, the question no backtest can answer for you.