S&P 500
Tracks roughly 500 of the largest publicly traded U.S. companies, weighted by market capitalization. Widely used as the primary benchmark for the overall U.S. stock market.
Operator
S&P Dow Jones Indices
Launched
1957
Country
United States
Methodology
Market-capitalization weighted; constituents are selected by a committee based on size, liquidity, and profitability criteria rather than a fixed mechanical rule.
How Investors Use This Index
The S&P 500 is the most commonly cited yardstick for U.S. equity performance — when a fund manager talks about 'beating the market,' this index is usually the benchmark being measured against. Because it's weighted by market capitalization, its largest constituents (the handful of companies with the biggest market values) have an outsized effect on its daily moves, so the index can rise even when most of its 500 members are flat or falling, as long as a few mega-caps are climbing. It also underlies some of the largest and most heavily traded index funds and ETFs in the world.
Major Sectors
Frequently Asked Questions
How often does the S&P 500 rebalance?
Quarterly, effective the third Friday of March, June, September, and December. Companies can also be added or removed between scheduled reviews following mergers, acquisitions, or bankruptcies.
Is the S&P 500 the same as "the stock market"?
No. It's a large-cap U.S. benchmark. It excludes small caps, which are tracked separately by the Russell 2000, and most international markets.
Can I invest directly in the S&P 500?
Not directly — exposure comes through index funds or ETFs designed to track it, rather than buying the index itself.
What's the difference between the S&P 500 and the Nasdaq Composite?
The S&P 500 spans 11 sectors across major U.S. exchanges; the Nasdaq Composite is exchange-specific and far more concentrated in technology.