Every start month in the real price history of S&P 500 — 393 of them, from Jan 1993 to Sep 2025.
Data as of September 10, 2026
Your result
of all 12-month windows since 1993, investing all at once finished ahead.
Half of the 393 windows ended further ahead than this.
Starting May 2008: $6,766 against $9,464.
Starting Feb 2009: $15,326 against $11,715.
Total return, dividends reinvested. Cash still waiting to be invested earns nothing. Prices to Sep 2026.
Each bar is one start month: how much more, or less, the lump sum was worth at the end of its 12 months. Select a bar to draw that window below.
| Start year | Windows | Lump sum won | Median gap |
|---|---|---|---|
| 1993 | 12 | 92% | +2.9% |
| 1994 | 12 | 83% | +5.9% |
| 1995 | 12 | 100% | +12.1% |
| 1996 | 12 | 100% | +10.2% |
| 1997 | 12 | 100% | +12.2% |
| 1998 | 12 | 100% | +6.6% |
| 1999 | 12 | 92% | +5.4% |
| 2000 | 12 | 17% | -7.0% |
| 2001 | 12 | 8% | -8.2% |
| 2002 | 12 | 33% | -4.9% |
| 2003 | 12 | 100% | +10.0% |
| 2004 | 12 | 100% | +3.0% |
| 2005 | 12 | 100% | +4.1% |
| 2006 | 12 | 100% | +5.9% |
| 2007 | 12 | 25% | -4.0% |
| 2008 | 12 | 17% | -19.5% |
| 2009 | 12 | 100% | +12.1% |
| 2010 | 12 | 92% | +8.2% |
| 2011 | 12 | 58% | +0.6% |
| 2012 | 12 | 100% | +8.5% |
| 2013 | 12 | 100% | +9.2% |
| 2014 | 12 | 100% | +5.2% |
| 2015 | 12 | 50% | 0.0% |
| 2016 | 12 | 100% | +7.9% |
| 2017 | 12 | 100% | +7.9% |
| 2018 | 12 | 67% | +3.0% |
| 2019 | 12 | 83% | +3.4% |
| 2020 | 12 | 92% | +15.3% |
| 2021 | 12 | 67% | +2.0% |
| 2022 | 12 | 50% | +0.7% |
| 2023 | 12 | 100% | +10.4% |
| 2024 | 12 | 100% | +6.0% |
| 2025 | 9 | 100% | +8.9% |
From Sep 2025 to Sep 2026: all at once ended at $11,657; the 12-month spread ended at $10,977.
| Month | All at once | 12-month spread | Money paid in |
|---|---|---|---|
| Sep 2025 | $10,000 | $833 | $833 |
| Oct 2025 | $10,238 | $1,687 | $1,667 |
| Nov 2025 | $10,258 | $2,523 | $2,500 |
| Dec 2025 | $10,267 | $3,358 | $3,333 |
| Jan 2026 | $10,418 | $4,241 | $4,167 |
| Feb 2026 | $10,328 | $5,038 | $5,000 |
| Mar 2026 | $9,818 | $5,623 | $5,833 |
| Apr 2026 | $10,849 | $7,047 | $6,667 |
| May 2026 | $11,420 | $8,251 | $7,500 |
| Jun 2026 | $11,303 | $8,999 | $8,333 |
| Jul 2026 | $11,307 | $9,836 | $9,167 |
| Aug 2026 | $11,610 | $10,933 | $10,000 |
| Sep 2026 | $11,657 | $10,977 | $10,000 |
Across 393 start months, a lump sum finished ahead 312 times and behind 81 times. The median gap was +5.9%: half of the 393 windows were wider than that, half narrower. The worst month to have gone all in was May 2008 ($6,766 against $9,464); the best was Feb 2009 ($15,326 against $11,715).
All of it computed from the same month-end closes the charts above draw — a description of what happened, not a forecast.
Open S&P 500 in the interactive backtest to try a different amount or a different number of months.
This backtest shows what happened to a real price series and nothing more. It excludes trading costs, spreads, currency conversion and tax, assumes cash waiting to be invested earns nothing, and cannot tell you what the next window will do. It is information, not investment advice.
My Financial Freedom Tracker follows the money you actually hold — holdings, cost basis, net worth and the plan behind them.
StartBudget, net worth, portfolio and your FIRE plan — all in one dashboard.
See every fall from a prior peak a stock or ETF has lived through, how many months recovery took, and what each drop would have done to your amount.
See the crash historyEnter your gain and how long you held it, then compare the tax across 28 countries ranked — with the holding-period rules that reorder the list.
Compare 28 countriesCalculate your path to financial independence with Coast FIRE, Barista FIRE, and custom withdrawal strategies.
Try the FIRE CalculatorProject net worth and cash flow across a whole life — add the car, the career break, the child and the pension, and see the year each one lands.
Open the Life PlannerFind the amount you need today so compound interest carries you to FIRE — no more contributions needed.
Find your Coast FIRE numberFind the portfolio size that lets you downshift to part-time work, with healthcare bridge costs built in.
Try Free Barista FIRE Calculator