The full month-by-month total-return series behind firenum's historical backtesting, derived from Robert Shiller's dataset and published as a tidy CSV and JSON. 1,848 rows, 1871–present. No sign-up.
CSV columns: year, month, nominalReturn · ~40 KB
What's in the Data
Each row is one month of nominal total return for the S&P 500 composite — price change plus reinvested dividends, expressed as a decimal (so 0.0173 means +1.73% for that month).
| year | month | nominalReturn |
|---|---|---|
| 1871 | 1 | -0.011335 |
| 1871 | 2 | 0.017316 |
| 1871 | 3 | -0.049547 |
| … | … | … |
| 2024 | 12 | 0.003321 |
Methodology
The series is derived from Robert J. Shiller's long-running historical dataset (the data behind Irrational Exuberance). Monthly total returns are computed from his S&P composite price and dividend series.
The returns are nominal, not CPI-adjusted. This is deliberate: when a projection already applies inflation to expenses — as firenum's does — nominal returns are the correct input, because using real returns would double-count inflation. If you need real returns, deflate by CPI yourself.
One caveat: pre-1926 figures are reconstructed from historical sources and are less precise than modern index data. They're standard for long-horizon backtesting, but treat the 19th-century tail as indicative rather than exact.
How firenum Uses It
The Fire Planner's historical backtesting runs your plan against every overlapping period since 1871 using exactly this series — about 1,260 periods for a 50-year projection — to report success rates and best- and worst-case outcomes. The full method is documented in the mathematical foundations guide.
How to Cite
If you use this data, please credit Robert Shiller as the original source. A suggested citation:
Shiller, Robert J. Online Data — U.S. Stock Markets 1871–Present. Yale University. Monthly nominal total returns prepared by firenum.com, firenum.com/tools/shiller-data.
Original source: Robert Shiller's Online Data page (Yale University). This dataset is offered for research and educational use; attribution is required.
Frequently Asked Questions
A flat table of monthly nominal total returns for the S&P 500 composite from January 1871 to the present—1,848 rows of year, month, and nominalReturn (a decimal, e.g. 0.0173 = +1.73%). Total return means price change plus reinvested dividends. Available as CSV and JSON.
These are nominal (not CPI-adjusted) returns. If you're modeling a plan that already applies inflation to expenses—as firenum's backtesting does—you want nominal returns, because using real returns would double-count inflation. If you need real returns, deflate by CPI separately.
It's derived from Robert J. Shiller's long-running "Online Data" set (Yale University), the same data behind his book Irrational Exuberance. We compute monthly total returns from his S&P composite price and dividend series. Please credit Shiller if you reuse it.
Pre-1926 figures are reconstructed from historical sources and are less precise than modern index data; Shiller's series stitches several sources together. It's the standard dataset for long-horizon backtesting, but treat the 19th-century tail as indicative rather than exact.
The Fire Planner's historical backtesting runs your plan against every overlapping period since 1871 using exactly this series—roughly 1,260 periods for a 50-year projection—to report success rates and best/worst-case outcomes.
Yes. It's offered for research and educational use. Attribute Robert J. Shiller as the source and, ideally, link back to this page. See the "How to cite" section above.
Looking for planning tools? See the FIRE spreadsheets & downloads or run a backtest in the Fire Planner.