What Is the Three-Fund Portfolio?
Is a portfolio better the more complex it is? The Bogleheads community answers that 'three indexes are enough.'
Getting Done with Three Indexes
The Three-Fund Portfolio is a simple combination widely used by the Bogleheads community, which follows John Bogle's philosophy. It is built from only three broad indexes.
① U.S. total stock market index ② International (developed + emerging) total stock market index ③ U.S. total bond market index
The key is that these three alone let you hold most of the world's stocks and bonds at low cost.
How to Set the Weights
There is no single fixed weighting; you adjust it by age and risk tolerance.
Young and aggressive: high stock weight (e.g., stocks 90 / bonds 10). Retirement / conservative: high bond weight (e.g., stocks 50 / bonds 50, or 40 / 60).
Within stocks, the international weight is usually about 20–40% of total stocks. For example, a combination like 'U.S. stocks 60% / international stocks 25% / bonds 15%' is a common example.
The weights above are only examples, not correct answers. You should adjust them to your own investment horizon and the drawdown you can bear.
Why Simplicity Is a Strength
The strengths of the three-fund approach are low cost, low maintenance, and broad diversification.
Because they are index funds, management fees are low, and with only three funds, rebalancing and management are easy. You do not need to pick stocks or predict the market, which reduces mistakes.
A downside would be that, because it tracks the market average, it does not try to beat the market, and it fully bears the drawdown of a downturn in proportion to its stock weight. Simplicity also means 'accepting the ups and downs together with the market.'
よくある質問
Q. With only three funds, is diversification enough?
Because each index holds thousands of stocks, just three indexes still spread across most of the world's stocks and bonds. Diversification is determined not by the 'number' of funds but by the 'number of holdings' inside them and the 'breadth of asset classes.'
Q. Is a three-fund portfolio safe even in a downturn?
No. It fully bears a downturn's drawdown in proportion to its stock weight. For example, a three-fund portfolio that is 80% stocks can suffer a substantial loss in a big bear market. The bond weight only cushions part of that shock.
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