S&P 500 Index
Historical returns and performance of the U.S. stock market benchmark
What is the S&P 500?
The S&P 500 (Standard & Poor's 500) is a stock market index tracking the performance of 500 of the largest publicly traded companies in the United States. It is widely regarded as the best single gauge of large-cap U.S. equities and covers approximately 80% of available U.S. market capitalization.
The index is market-cap weighted, meaning larger companies like Apple, Microsoft, and Amazon have a greater influence on the index's performance than smaller companies.
On StocksBio, we use SPY (SPDR S&P 500 ETF Trust) as our S&P 500 benchmark. SPY is the oldest and most liquid ETF that tracks the S&P 500 index, with an expense ratio of just 0.09%.
Major US Stock Market Indices
Compare the S&P 500 to other key US market benchmarks
500 largest US companies
100 largest non-financial NASDAQ stocks
30 blue-chip industrial companies
2000 small-cap US companies
Entire US stock market
S&P 500 Historical Returns
Based on SPY ETF data. $1,000 invested at the start of each period.
S&P 500 CAGR (Compound Annual Growth Rate)
The S&P 500's long-term average annual return (CAGR) has historically been around 10% before inflation, or roughly 7% after adjusting for inflation. This makes it a common benchmark for evaluating individual stock and portfolio performance.
S&P 500 Monthly Statistics
Compare Stocks vs S&P 500
See how individual stocks have performed against the market benchmark
Understanding the S&P 500
How is the S&P 500 Calculated?
The S&P 500 is a market-capitalization-weighted index. This means each company's weight in the index is proportional to its total market value (share price × shares outstanding). As of 2026, the top 10 companies make up over 30% of the entire index.
S&P 500 Sectors
The index includes companies from all 11 GICS sectors: Technology, Healthcare, Financials, Consumer Discretionary, Communication Services, Industrials, Consumer Staples, Energy, Utilities, Real Estate, and Materials. Technology is typically the largest sector by weight.
Why Use the S&P 500 as a Benchmark?
The S&P 500 is the most commonly used benchmark for U.S. equity performance because:
- It covers ~80% of U.S. market capitalization
- It includes companies across all sectors
- It has a long track record (dating back to 1957)
- It's easily investable through ETFs like SPY, VOO, and IVV
SPY vs the S&P 500 Index
On StocksBio, we use SPY (SPDR S&P 500 ETF Trust) data for our S&P 500 calculations. SPY tracks the S&P 500 index very closely but has a small expense ratio of 0.09% per year. Over very long periods (20+ years), this may cause SPY to slightly underperform the actual index by approximately 1-2% total.