A video refers to Buffett’s 10-year bet against the S&P 500 as a lesson about short-term trading. This article checks the result against Berkshire Hathaway’s letter and compares it with Thai fund data, while explaining limits on what can be inferred.
What the source material says
The saved transcript describes Warren Buffett betting against fund managers who tried to beat the S&P 500 over ten years, and presents it as a lesson about long-term investing. The ASR transcript is short and contains errors.
What did Berkshire Hathaway record about the bet?
Buffett’s bet with Protégé Partners compared a fund of five hedge funds with an S&P 500 index fund over the ten years ending in 2017. It was not a randomized study of all investors or a direct comparison between “people who trade every day” and index-fund buyers. Berkshire’s 2017 letter reports average annual returns of 0.3%–6.5% for the five funds and 8.5% for the S&P index fund during the period. See Berkshire Hathaway’s 2017 shareholder letter, pages 9–11 for the bet, results, and fee discussion.
The supported lesson is the result for that example and period. It does not show that every actively managed fund loses every year, or that buying the S&P 500 guarantees a profit.
Compare funds for the same market and period
SPIVA Asia Ex-Japan Year-End 2025 reports that about three quarters of Thai large-cap equity funds underperformed the S&P Thailand BMI in 2025. That comparison refers to one category and period. It is not the S&P 500 and does not describe the return of an individual fund or investor. See SPIVA and Persistence Scorecards, checking the market, fund category, and end date in each report.
Checklist before comparing funds
- Mandate and holdings: What does the fund invest in, and which index is the comparison benchmark?
- Time period: Are the periods the same, and do they include both rising and falling markets?
- Costs: Compare fund fees and trading costs with the returns shown.
- Risk and currency: Overseas funds may involve exchange-rate risk and different trading conditions.
- Fit with your goal: When will you need the money, and how much decline in value can you tolerate?
Thailand’s SEC recommends reviewing a Fund Fact Sheet, which summarizes risk level, policy, performance, trading terms, fees, and major holdings. Read the guide to reading a Fund Fact Sheet and check funds in SEC Fund Check.
This article does not recommend an index fund or any other fund for a specific person. Past returns and one bet cannot guarantee future performance.