Rolling returns
"A long-run average of 7% a year" hides more than it reveals. This chart slices history into every possible N-year window and shows the real annualized return of each: over 1-year windows the outcome looks like a coin flip; over 20-year windows the best and worst cases squeeze into a much narrower band.
The horizontal axis is each window's starting year; the vertical axis is that window's annualized real return. Stretch the holding period and watch the worst case rise — this is the raw evidence behind "time diversifies risk," and also its limit: even at 20 years, the worst window is not guaranteed to be positive.
Rolling window
Key readings
- Ending real purchasing power (from 10,000)
- $1,365,219
- Deepest drawdown
- −35.2% (1972-1974)
- Longest underwater period
- 13 years (1972-1985)
- Worst / best 10-year window
- −2.7% (1972) / +12.1% (1989)
- Median window
- +5.2%
Data and limits
Rolling windows overlap heavily, so they are not independent samples — do not read the spread as a probability distribution. The sample is one century of one history: it has rehearsed many scripts, but not all of them.
Portfolio math assumes annual rebalancing.
Data are annual real (inflation-adjusted) returns; sources and definitions are documented in "Where the chart data comes from" on the methodology page. methodology page
Everything above is computed from historical data and your inputs. History does not guarantee the future. Not investment advice.
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