What Is an Index Fund?
Index funds are one of the most important inventions in personal finance — and one of the most widely recommended tools for everyday investors. This lesson explains what they are, why they work, and why even professional investors rarely beat them.
The problem with picking individual stocks
Picking the right stock requires predicting the future better than millions of other investors. Research shows most professional fund managers fail to beat the market average over 10+ year periods. For individuals without the same tools, the odds are even lower.
Index funds offer a different approach: instead of trying to pick winners, buy a little bit of everything and capture the average return of the entire market.
What an index is
An index is a list of stocks grouped by some rule. The S&P 500 is an index of the 500 largest publicly traded US companies. When you invest in an index fund, you buy a fund tracking one of these lists — owning a small piece of every company on it.
Tracks the 500 largest US companies. One fund = Apple, Amazon, Microsoft, and 497 others.
Tracks nearly all publicly traded US companies — thousands in one fund.
Why index funds tend to outperform active funds
Every dollar you pay in fees is a dollar that doesn't compound. Actively managed funds often charge 1%+ per year. Index funds often charge 0.03%–0.10%. Over 30 years, a 1% annual fee difference on $10,000 can cost over $30,000 in lost growth.
Add that most active managers underperform their benchmark index after fees, and the case for index funds becomes very strong for most individual investors.
How to actually invest in one
Index funds are available through brokerage accounts — online investment accounts at companies like Fidelity, Vanguard, or Schwab. Many also come as ETFs (Exchange-Traded Funds) that trade throughout the day like stocks. Many have no minimum investment.
An index fund charges 0.05%/year. An active fund charges 1.2%/year. On $5,000, what's the fee difference in year one?
Recap
- An index fund buys a little of every stock in a list, rather than trying to pick winners.
- Index funds typically outperform active funds over long periods, mainly due to lower fees.
- The S&P 500 is the most common benchmark — one fund gives exposure to 500 large US companies.
- Next up: risk and time horizon — the two factors that determine how to invest.