ArthaPilot Research
What U.S. market history shows when the full investment is available on day one.
Published 2026-07-28
Data through July 2026
We compared $100,000 invested at once with 12 equal monthly purchases across every eligible month-end in extended U.S. large-cap history. Each pair used the same 10-year end date, and cash waiting to be invested earned the historical Treasury-bill return.
Immediate investment finished ahead in 67.2% of 1,081 rolling periods. Its average annualized edge was 0.25 percentage points, and the median ending-wealth advantage was $7,181. DCA led in 32.8% of periods.
The periods overlap and come from one realized U.S. market history. They describe the historical record; they are not independent trials or a forecast of the next investor's outcome.
Finished ahead
67.2%
Investing immediately
Average annualized gap
+0.25 percentage points
Immediate investment minus DCA
Median ending-wealth gap
+$7,181
Over 10 years
Immediate investment benefited from putting all available cash into a market that rose more often than it fell. DCA left part of the balance waiting during deployment, which usually gave up some of that return.
The pattern reversed when prices fell soon after the start. Later DCA purchases then bought more shares at lower prices. Longer purchase schedules widened the cost of waiting in rising periods; interest on waiting cash narrowed it.
For cash already available on day one, investing immediately had the higher historical win rate. DCA exchanged some expected market exposure for protection against a decline during the first months.
This study does not cover periodic income invested as it is earned, multi-asset portfolios, taxes, trading costs, or plans that change after a loss.
The study uses SPY.SIM, with monthly extended U.S. large-cap total returns from July 1926 through July 2026. See the .SIM methodology for how the extended history is constructed.
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