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S&P 500 Index Funds Explained
S&P 500 index funds track the 500 largest publicly traded US companies, offering broad exposure to large-cap US stocks through a single, low-cost investment.
Why the S&P 500 Is So Popular
The S&P 500 represents roughly 80% of total US stock market value and has a long historical track record, making it a common benchmark and a popular core holding for long-term investors.
Popular S&P 500 Funds
| Fund | Expense Ratio | Structure |
|---|---|---|
| Vanguard S&P 500 ETF (VOO) | 0.03% | ETF |
| Vanguard 500 Index (VFIAX) | 0.04% | Mutual fund |
| Fidelity 500 Index (FXAIX) | 0.015% | Mutual fund |
S&P 500 Only vs. Total Market
The S&P 500 excludes smaller US companies that a "total market" fund (like VTI) would include — the difference in actual returns has historically been fairly small, though total market funds offer marginally broader diversification.
Common Mistakes
Assuming the S&P 500 alone provides complete diversification — it's exclusively large-cap US companies, missing small/mid-cap and international exposure that a broader portfolio might include.
Frequently Asked Questions
It provides strong large-cap US exposure but misses smaller US companies and international markets — many investors pair it with additional funds for broader diversification.
Both track the S&P 500 with nearly identical low costs — VOO is an ETF (trades throughout the day), while VFIAX is a mutual fund (trades once daily at end-of-day price).