PORTFOLIO COMPARISON / ONE VARIABLE

Buffett 90/10 Portfolio Backtest

Backtest a transparent Buffett 90/10 ETF proxy: 90% S&P 500 exposure and 10% short-term Treasuries, compared with a conventional 60/40 allocation.

Warren Buffett shareholder-letter allocationFrequently cited simple allocation90% S&P 500 / 10% short TreasuriesLed its reference in this test

HISTORICAL BACKTEST RESULT

60% VOO / 40% SHY vs 90% VOO / 10% SHY

60% VOO / 40% SHY 90% VOO / 10% SHY
2020-06-02 → 2026-07-31 · 1542 common sessions
60% VOO / 40% SHY$17,1559.2% annualized · -17.3% max drawdown
90% VOO / 10% SHY$22,30913.9% annualized · -23.4% max drawdown

Historical calculation from cached Marketstack EOD data. Annual rebalancing, $10,000 initial value, nominal USD before fees and taxes. The disclosed portfolio definitions—not an AI model—produce the result.

RUN THIS PORTFOLIO

Change the rule, then compare the new result.

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WHAT TO COMPARE

Read the trade-off as a system.

  1. 01Ending value
  2. 02Maximum drawdown
  3. 03Annualized return
  4. 04Recovery path

WHEN TO LOOK

Locate where the difference appeared.

First common ETF observation onwardEquity drawdownsRate shocksRecent market leadership

A useful comparison shows whether an advantage was broad or created by one unusually favorable period. Review the portfolio backtest methodology to understand how the same rules are applied across a shared data window.

PORTFOLIO RULE / DISCLOSED IMPLEMENTATION

Transparent 90/10 ETF proxy

The commonly cited 90/10 instruction came from Warren Buffett’s 2013 shareholder letter. This page discloses the liquid ETF proxy and every implementation choice.

VOOVanguard S&P 500 ETFVanguard S&P 500 ETFUS large-cap equity ETFTracks the S&P 500 through a low-cost index ETF.90%S&P 500 index ETF
SHYiShares 1–3 Year Treasury Bond ETFiShares 1–3 Year Treasury Bond ETFShort-term Treasury ETFHolds short-duration US Treasury bonds.10%Short-term Treasury ETF

REBALANCINGAnnual rebalancing to 90% equities and 10% short-term Treasuries.

DATA WINDOWThe calculation uses the first shared Marketstack EOD date for VOO and SHY. It is an ETF implementation, not an index reconstruction.

STRATEGY CONTEXT

What this portfolio strategy means.

A short definition, the reason investors return to it, and the historical context behind the name. It is context for a backtest—not an investment recommendation.

What it is

The Buffett 90/10 portfolio is a simple allocation of 90% broad US stock-market exposure and 10% short-term government bonds. On this page it is implemented with a disclosed S&P 500 ETF and short-term Treasury ETF, then compared with a 60/40 reference. The test measures the added equity exposure; it does not treat the name as a personalized allocation recommendation.

Why investors use it

The rule is compelling because it is concise, low-maintenance, and makes the central trade-off unmistakable: most of the account participates in equity-market gains and losses, while a small Treasury sleeve provides a more stable component. It gives investors a useful counterpoint to balanced portfolios when assessing how much drawdown and path risk they accepted for a higher equity weight.

Historical context

The phrase became widely known after Warren Buffett wrote in Berkshire Hathaway’s 2013 shareholder letter that the trustee for his wife should hold 90% in a very low-cost S&P 500 index fund and 10% in short-term government bonds. That instruction was specific to an estate-plan context. This page records a liquid ETF proxy and the available market window instead of extending the result backward as if it were the original instruction.