The S&P 500 is the most widely quoted stock market benchmark in the world. Here's what it is, how it works, and how to invest in it.
When people say "the market is up 1.5% today," they almost always mean the S&P 500. It's the most widely quoted benchmark in investing — referenced on every financial news channel, in every brokerage app, and in most retirement account summaries. But what exactly is it?
This guide answers that question clearly — no jargon, no assumptions.
The S&P 500 (formally: Standard & Poor's 500) is an index that tracks the stock performance of 500 large U.S. companies. Think of it as a weighted average of the stock prices of 500 of the biggest, most established businesses in America.
It includes companies you interact with daily: Apple, Amazon, Microsoft, JPMorgan Chase, ExxonMobil. If a company is publicly traded, large, and U.S.-based, there's a good chance it's in the index.
The S&P 500 is maintained by S&P Dow Jones Indices, a joint venture between S&P Global, CME Group, and News Corp. They set the rules for which companies qualify and update the index accordingly.
It's one of three major U.S. stock market indexes, alongside the Dow Jones Industrial Average (30 stocks) and the Nasdaq Composite (tech-heavy, ~3,000 stocks). The S&P 500 sits in the middle — broad enough to represent the market, focused enough to be meaningful.
A committee at S&P Dow Jones Indices decides which companies make the cut. To qualify, a company must meet several criteria:
The committee meets regularly and removes companies that no longer qualify or adds new ones that do. On average, 20–25 companies turn over per year.
The S&P 500 is market-cap weighted. That means larger companies have more influence on the index's daily movement than smaller ones.
Apple has a market cap of roughly $3 trillion. A small S&P 500 member with a $20 billion market cap has almost no influence. When Apple moves 2%, the index feels it. When a smaller company moves 5%, most investors barely notice.
This weighting means the S&P 500 is heavily influenced by its top 10 holdings — which collectively make up about 30–35% of the entire index.
| Company | Ticker | Approximate Weight | |---|---|---| | Apple | AAPL | ~7% | | Microsoft | MSFT | ~6% | | NVIDIA | NVDA | ~6% | | Amazon | AMZN | ~4% | | Alphabet (Google) | GOOGL/GOOG | ~4% | | Meta Platforms | META | ~2.5% | | Berkshire Hathaway | BRK.B | ~1.7% | | Eli Lilly | LLY | ~1.5% | | Broadcom | AVGO | ~1.5% | | JPMorgan Chase | JPM | ~1.5% |
Holdings and weights change as stock prices fluctuate and the index is rebalanced.
The S&P 500 serves three roles in investing:
It's the yardstick everyone uses. When a mutual fund or ETF claims strong performance, analysts ask: "compared to the S&P 500?" Most actively managed funds fail to beat it consistently over 10+ year periods — which is why index investing has become so popular.
The S&P 500 is widely considered the best single measure of the health of the U.S. stock market. When it drops 20%, that's a bear market. When it rises 20%+ from a low, that's a bull market.
You can't invest directly in the index — it's just a list with math. But you can invest in funds that track it almost perfectly. These funds hold all 500 stocks in roughly the same weights as the index.
Several fund families offer S&P 500 index funds with very low expense ratios:
These funds buy and hold all 500 stocks in proportion to their index weights. They rebalance automatically when the index changes.
ETFs (exchange-traded funds) that track the S&P 500 work similarly but trade like stocks throughout the day:
For most buy-and-hold investors, the mutual fund or ETF choice doesn't matter much. The expense ratio is what matters — lower is better, and all the options above are very low.
The S&P 500 has delivered strong long-term returns, despite dramatic short-term volatility:
| Period | Average Annual Return (approximate) | |---|---| | Last 10 years (2014–2024) | ~12–13% | | Last 30 years (1994–2024) | ~10–11% | | Since inception (1957–present) | ~10% |
These are nominal returns before inflation. Real (inflation-adjusted) returns average roughly 7–8%.
Important caveat: Past performance doesn't guarantee future results. The S&P 500 fell 38% in 2008, 19% in 2022, and 34% in the COVID crash of March 2020 — only to recover and reach new highs. Long-term investors who stayed invested captured all of the recovery.
The S&P 500 spans 11 sectors, giving investors automatic diversification across the U.S. economy:
| Sector | Approx. Weight | |---|---| | Information Technology | ~29% | | Financials | ~13% | | Healthcare | ~12% | | Consumer Discretionary | ~10% | | Industrials | ~9% | | Communication Services | ~9% | | Consumer Staples | ~6% | | Energy | ~4% | | Real Estate | ~2.5% | | Materials | ~2.5% | | Utilities | ~2.5% |
Tech dominates — which means when tech has a rough year (like 2022), the S&P 500 tends to underperform compared to more diversified global indexes.
A common question: should I invest in the S&P 500 or a total market index fund?
The total market (tracked by funds like VTSAX or FSKAX) includes everything the S&P 500 does, plus mid-cap and small-cap stocks — roughly 3,500–4,000 companies total instead of 500.
The practical difference is small:
Neither is wrong. Most serious long-term investors are comfortable with either.
Is the S&P 500 the whole stock market? No. It's the 500 largest U.S. companies by market cap. The U.S. stock market has roughly 4,000–5,000 publicly traded companies. The S&P 500 captures about 80% of total U.S. market capitalization, which is why it's such a useful proxy.
Does the S&P 500 include international stocks? No. It's U.S.-only. For global diversification, you'd need a separate international or world index fund (like VGTSX or VEU).
Can individual stocks leave the S&P 500? Yes. Companies are added and removed regularly. Reasons for removal include market cap falling below the threshold, a company going private, merging with another company, or failing the profitability requirements.
What's the difference between S&P 500 and the Dow? The Dow Jones Industrial Average tracks only 30 large U.S. companies and is price-weighted (not market-cap weighted). It's less representative of the broader market. The S&P 500 is the more widely used professional benchmark.
The S&P 500 is the most important stock market benchmark in the world. It's a reasonable proxy for U.S. large-cap equity performance, and investing in an S&P 500 index fund — with its low costs and automatic diversification — is one of the most straightforward paths to building long-term wealth.
If you're comparing specific funds that track the S&P 500, use our comparison tool to see expense ratios, returns, and how funds like VFIAX vs FXAIX stack up side by side.
This article is for educational purposes only. Past performance does not guarantee future results. Consult a qualified financial advisor before making investment decisions.
