🎯 In 30 seconds: A full portfolio can be one, two or three broad index funds. Fewer funds means less to manage but less control. More funds means a little more work and the ability to tune each piece. All three setups below own thousands of companies, cost very little, and avoid the most common trap, which is owning ten overlapping funds that add up to nothing in particular.
Why simple works
A broad index fund already holds most of the market. Adding a fourth or fifth fund usually means owning the same big companies again under a different label. Each extra fund is one more thing to rebalance and one more expense ratio to check.
Simple also helps behavior. A portfolio you understand in one sentence is easier to hold through a crash than one you built from twenty recommendations. The behavior gap page shows what the opposite costs.
The three simple setups
| Setup | What you hold | Who does the rebalancing | What you give up |
|---|---|---|---|
| One fund: target-date | A single fund holding US stocks, foreign stocks and bonds, getting more conservative each year | The fund | Control over the mix and the pace of change; costs vary widely between fund families |
| One fund: balanced | A single fund with a fixed mix, such as 60% stocks and 40% bonds | The fund | The mix never changes as you age unless you switch funds |
| Two funds | A total world stock fund plus a total bond fund | You, once a year | Fine-tuning of the US vs foreign split |
| Three funds | A total US stock fund, a total international stock fund and a total bond fund | You, once a year | A little simplicity; you now set three numbers |
Example mixes
These are illustrations of how people commonly set the dials, not advice for any one person. The stock share usually drops as the goal gets closer. See Asset allocation for how to choose your own.
| Example investor | US stocks | International stocks | Bonds |
|---|---|---|---|
| Long horizon, comfortable with big swings | 56% | 24% | 20% |
| Middle ground | 42% | 18% | 40% |
| Near or in retirement | 28% | 12% | 60% |
In each row, international stocks are 30% of the stock portion. Some people hold none abroad, some match the world market (about a third outside the US). The International investing page covers that choice.
Worked example: rebalancing a three-fund portfolio
Priya, 30, puts $10,000 into the first row’s mix: $5,600 US stocks, $2,400 international stocks, $2,000 bonds. A year later US stocks are up 20%, international up 5% and bonds up 3%.
| Fund | After a year | Target share | Target amount | Action |
|---|---|---|---|---|
| US stocks | $6,720 | 56% | $6,328 | Sell $392 |
| International | $2,520 | 24% | $2,712 | Buy $192 |
| Bonds | $2,060 | 20% | $2,260 | Buy $200 |
| Total | $11,300 | 100% | $11,300 |
Inside an IRA or 401(k) that trade costs nothing in tax. In a taxable account she could instead aim her next few months of contributions at the two funds that are behind, and sell nothing.
What it costs
With three index funds the overall cost is a weighted average of their expense ratios. Using example ratios of 0.04%, 0.08% and 0.05%:
| US stocks: 56% × 0.04% | 0.0224% |
| International: 24% × 0.08% | 0.0192% |
| Bonds: 20% × 0.05% | 0.0100% |
| Blended cost | About 0.05% a year, or about $5 on $10,000 |
| Same $10,000 in a fund charging 0.50% | $50 a year |
The ratios above are examples. Real ones are listed on each fund’s fact sheet and prospectus, and FINRA’s free Fund Analyzer compares them.
Choosing between them
- Pick one fund if you know you will not rebalance, or if all your money is in one account. Target-date funds are built for this.
- Pick two or three funds if you hold several accounts. You can place bonds in one account and stocks in another and still hit your overall mix (see Which account first, and what goes where).
- Do not mix a target-date fund with other funds unless you mean to. The target-date fund is designed to be the whole portfolio, so adding more funds changes its mix in ways that are hard to track.
- Test the mix in the Backtest tool and look at the worst year, not just the average.
- What does a two-fund portfolio usually hold? Answer: A total world stock fund and a total bond fund.
- In Priya’s example, why does she sell US stocks? Answer: They grew past their 56% target to $6,720 against a target of $6,328.
- Why is pairing a target-date fund with other funds a problem? Answer: The target-date fund is built to be the whole portfolio, so extra funds throw off its mix.
- How do you find the blended cost of three funds? Answer: Multiply each expense ratio by its share of the portfolio and add them up.