Everything you need to know about index funds: how they work, why they outperform most alternatives, and how to use them for wealth building.
- If you could only learn one thing about investing, it should be this: a low-cost index fund, held for the long term, is likely to outperform the vast majority of professional fund managers.
- But attempting to avoid downturns by timing the market is a strategy that consistently fails for both individual and professional investors.
- This is not a contrarian opinion or a fringe theory.
If you could only learn one thing about investing, it should be this: a low-cost index fund, held for the long term, is likely to outperform the vast majority of professional fund managers. This is not a contrarian opinion or a fringe theory. It is one of the most well-established facts in all of finance, backed by decades of data and endorsed by many of the world’s most respected investors.
The Core Idea
An index fund does not try to beat the market. It tries to be the market. By holding every stock in a given index, such as the S&P 500 or the total U.S. stock market, the fund delivers the market’s return minus a tiny fee. This approach is called passive investing because there is no fund manager making active decisions about which stocks to buy or sell.
This simplicity is its greatest strength. No research team to pay. No trading costs from frequent buying and selling. No human judgment to introduce errors. The fund simply tracks its index as faithfully as possible and passes the returns through to investors.
Why They Win
The data on index fund performance is overwhelming. Over any 15-year period, roughly 85 to 90 percent of actively managed large-cap funds fail to beat the S&P 500 index. Over 20 years, the failure rate climbs even higher. The small minority of active funds that do outperform in one period rarely sustain that outperformance in subsequent periods. Picking the winning active fund in advance is essentially a gamble.
The primary reason active funds lose is cost. The average actively managed equity fund charges an expense ratio of around 0.50% to 1.00% per year. An index fund charges 0.03% to 0.10%. That fee drag, compounded over decades, creates a hurdle that most active managers cannot clear. Before fees, the average active fund roughly matches the market. After fees, it falls short.
Types of Index Funds
Index funds exist for virtually every corner of the financial markets. Total U.S. stock market funds provide the broadest domestic exposure. S&P 500 funds focus on the 500 largest U.S. companies. International stock funds cover developed markets outside the U.S. Emerging market funds cover developing economies. Bond index funds track various segments of the fixed-income market. And sector-specific index funds focus on particular industries.
For most people, a combination of a total U.S. stock market fund, an international stock fund, and a bond fund provides all the diversification needed. This three-fund approach covers thousands of stocks and bonds across the globe in just three holdings.
The Role of Time
Index investing is a long-term strategy. In any given year, the stock market might rise 25% or fall 30%. These short-term fluctuations are unpredictable and irrelevant to the long-term investor. What matters is the long-term trajectory, which has been consistently upward over every meaningful time horizon. The average annual return of the U.S. stock market over the past century is approximately 10% before inflation, or about 7% after inflation.
This means an index fund investor who stays invested through the ups and downs has historically doubled their money roughly every ten years in real terms. The key word is stays. Investors who panic and sell during downturns lock in losses and miss the recovery. The index fund strategy only works if you can maintain the discipline to stay invested.
Common Objections
The most common objection to index investing is that it is boring. This is true, and that is the point. Exciting investing strategies usually involve higher fees, more risk, and worse outcomes for the average investor. Boring and effective is a better combination than exciting and expensive.
Another objection is that index funds cannot protect you from market downturns. This is also true. When the market falls, your index fund falls with it. But attempting to avoid downturns by timing the market is a strategy that consistently fails for both individual and professional investors. Missing just the ten best market days over a 20-year period can cut your total return in half. Those best days often occur immediately after the worst days, making them impossible to capture if you are sitting on the sidelines.
Getting Started
Buy a total stock market index fund with the lowest expense ratio you can find. Set up automatic monthly contributions. Ignore market news. Check your portfolio once or twice a year. Rebalance if needed. Repeat for 20 to 30 years. This strategy, while unglamorous, has built more wealth for more people than any other approach in the history of investing.
All investments carry risk, including loss of principal. Past performance does not guarantee future results. See our financial disclaimer for important disclosures.
A worked example
Imagine investing $500/month for 30 years at an average 8% annual return. Total contributions: $180,000. Final balance: roughly $745,000. The first $180,000 is yours; the other $565,000 is compounded growth. Now imagine starting 10 years later - same $500/month for 20 years at 8%: contributions $120,000, balance $295,000. The 10 years cost you about $450,000 in foregone growth. Time in the market beats timing the market by an enormous margin.
Common mistakes to avoid
- Trying to time the market. Studies consistently show that missing just the 10 best market days over 20 years cuts returns roughly in half. You can't reliably know which days those will be.
- Picking individual stocks based on news or tips. By the time it's news, the price already reflects it. Index funds aren't exciting but they outperform most retail stock-picking by a wide margin.
- Panic-selling in a downturn. Selling locks in losses. Markets have always recovered. The investors who do worst are the ones who sell low and re-buy high.
Frequently asked questions
How much money do I need to start investing?
Less than you think. Most major brokerages (Fidelity, Schwab, Vanguard) have no minimum balance. Fractional shares mean you can buy a $1 slice of any stock or ETF. Realistically, $50-100/month into a low-cost index fund is enough to start building real wealth over decades.
Is it too late to start investing at 40, 50, or 60?
No - but the strategy changes. At 40 you still have 25 years of compounding ahead. At 50 the focus shifts to maximizing 401(k) contributions (you can contribute extra after age 50). At 60 it's about preserving what you have and shifting to a more conservative allocation. The worst day to start was 20 years ago; the second-best is today.
Should I invest in individual stocks or index funds?
Index funds for nearly everyone. Over 20-year periods, 80%+ of professional fund managers fail to beat the index - and they have PhD analysts and millions in research budgets. A target-date retirement fund or a total-market index ETF will outperform what almost any retail investor can do picking individual stocks.
What is the safest investment?
FDIC-insured savings accounts and CDs (up to $250,000 per bank per ownership type) and US Treasury bills/bonds are the safest. They won't make you rich but they won't lose principal. For real (inflation-adjusted) safety, TIPS and I-Bonds protect against inflation, which traditional bonds don't.
How much should I have in stocks vs bonds?
A starting heuristic is 'your age in bonds' - so a 30-year-old holds 70% stocks / 30% bonds. Many financial planners now suggest something more aggressive given longer lifespans: 110 or 120 minus your age in stocks. Target-date funds do this automatically based on your retirement year.
Where this guide fits in
This article is part of the Chase The Dollar editorial library of practical money guides. We update guides as rules and rates change. If you spot a mistake or want us to cover a topic, the contact form is the fastest way to reach us.