You have a sum of money and you want it in the market. Do you invest it all at once, or feed it in gradually -- dollar-cost averaging -- so you don't buy right before a crash?
It's one of investing's oldest arguments, and it's answerable with data. So I ran it against every starting month of the S&P 500 from 1950 to 2025: deploy the whole amount now, or spread it evenly over the next few months, then compare which ended up ahead.
The headline result
Investing a lump sum beat spreading it over a year 76% of the time (S&P 500 total return, 1950-2025). And the longer you dragged the money in, the more often the lump won:
| How long the money was spread in | Lump sum won | DCA won |
|---|---|---|
| 6 months | 72.4% | 27.6% |
| 1 year | 76.2% | 23.8% |
| 2 years | 82.7% | 17.3% |
| 3 years | 86.3% | 13.7% |
The reason is mundane: the market goes up more often than it goes down, so money sitting on the sidelines waiting to be invested is money missing the average day's gain. On a concrete $10,000 deployed over a year, the lump sum finished about $607 ahead on average.
But averages hide the interesting part
Dollar-cost averaging lost the typical year. But when it won, it won for one reason: the market fell right after you started. Sort every one-year period by how much DCA beat the lump sum, and the top of the list isn't scattered across history -- it bunches up in one place.
The single best month to have been averaging in slowly rather than all at once was August 2008, on the eve of the financial crisis. DCA finished about 30 points ahead there, because each later purchase bought in cheaper as the market collapsed. The runners-up are the other months of 2007 and 2008.
So the honest reading: dollar-cost averaging is not a way to earn more, it's a way to be wrong by less when your timing is unlucky. You're trading a bit of expected return -- that ~$607 on $10,000 -- for protection against the one scenario everyone fears, putting it all in at the top. Whether that trade is worth it is about temperament, not math.
How it was measured
Like-for-like: both strategies invest the same total. The lump goes in at month zero; the DCA version splits it into equal monthly buys and both are compared at the end of the window, when both are fully invested. I used S&P 500 total return (dividends reinvested), and assumed the not-yet-invested DCA cash earns nothing (the conservative, common assumption). Every ending value is a real historical outcome, run for every start month 1950-2025, then tallied.
One scope note: this is the classic "deploy a windfall now vs later" question, not regular saving from a paycheck. If you invest each month as you earn it, you're already dollar-cost averaging by necessity -- there's no lump sum to compare against.
Check it yourself
The whole study is built on a monthly S&P 500 total-return index, and you can spot-check any single period in the two free, browser-based calculators it links to:
- Full write-up with the interactive chart: Dollar-Cost Averaging vs Lump Sum
- Dollar-Cost Averaging Calculator -- backtest investing a fixed amount every month
- S&P 500 Return Calculator -- what a lump sum would have grown to
Past performance doesn't predict the future; this is history, not advice.
Top comments (1)
The key result is quite compelling: across monthly starting points from 1950–2025, lump-sum investing beat spreading the same money over 12 months 76.2% of the time, with the advantage increasing as the DCA period gets longer.