US Stock Market Indices Guide
A comprehensive comparison of the 5 major US stock market indices — their constituents, historical returns, and when to use each one.
What Are Stock Market Indices?
A stock market index is a measurement of a section of the stock market. It tracks the performance of a specific group of stocks, providing a snapshot of how that segment of the market is performing.
Indices serve several important purposes:
- Benchmarking — Measure your portfolio's performance against the market
- Market health indicator — Gauge overall market sentiment and trends
- Investment vehicles — ETFs and index funds track these indices for passive investing
The five major US indices each capture different segments of the market, from large-cap blue chips to small-cap growth stocks.
Head-to-Head Comparison
| Index | Stocks | Focus | 1Y Return | 5Y Return | 10Y Return | Volatility |
|---|---|---|---|---|---|---|
| SPY S&P 500 SPY | 500 | Large-cap blend | +19.4% | +78.5% | +278.4% | 11.6% |
| QQQ NASDAQ 100 QQQ | 100 | Large-cap growth (tech-heavy) | +27.1% | +91.4% | +482.6% | 14.3% |
| DIA Dow Jones DIA | 30 | Large-cap value (blue-chip) | +12.6% | +53.9% | +221.1% | 12.0% |
| IWM Russell 2000 IWM | 2,000 | Small-cap blend | +24.7% | +18.5% | +153.0% | 19.2% |
| VTI Total US Market VTI | 4,000 | All-cap blend | +19.7% | +68.8% | +265.2% | 12.2% |
* Volatility is 3-year annualized standard deviation. Returns are total returns (not annualized).
Growth of $10,000 (10 Years)
How would $10,000 invested in 2014 have grown in each index?
Understanding Each Index
S&P 500
The benchmark for US large-cap stocks
The S&P 500 tracks 500 of the largest US companies, representing approximately 80% of US market capitalization. It's market-cap weighted, so larger companies like Apple, Microsoft, and Amazon have greater influence.
Best for: Investors seeking broad exposure to large-cap US stocks with a long track record. The most commonly used benchmark for portfolio performance.
Key characteristics: Diversified across all 11 sectors, moderate volatility, ~10% historical average annual return.
NASDAQ 100
Tech-heavy growth index
The NASDAQ 100 tracks the 100 largest non-financial companies listed on the NASDAQ exchange. It's heavily weighted toward technology (around 50% of the index), making it more volatile but with higher growth potential.
Best for: Investors bullish on technology and growth stocks who can tolerate higher volatility.
Key characteristics: Tech-heavy, higher growth potential, higher volatility, excludes financial sector.
Dow Jones Industrial Average
30 blue-chip industry leaders
The Dow Jones is the oldest US stock index, tracking 30 large, well-established "blue-chip" companies. Unlike other indices, it's price-weighted (not market-cap weighted), so higher-priced stocks have more influence.
Best for: Investors seeking exposure to established, dividend-paying industry leaders with lower volatility.
Key characteristics: Only 30 stocks, price-weighted, value-oriented, lower volatility than S&P 500.
Russell 2000
Small-cap US companies
The Russell 2000 tracks 2,000 small-cap US companies (the smallest companies in the Russell 3000 index). Small-caps offer higher growth potential but come with higher volatility and risk.
Best for: Investors seeking small-cap exposure for diversification or who believe small companies will outperform.
Key characteristics: Small-cap focus, higher volatility, can outperform in economic expansions, more domestic revenue exposure.
Total US Stock Market
The entire US market in one index
The Total US Stock Market index (tracked by VTI) includes virtually all publicly traded US companies — over 4,000 stocks across large, mid, and small caps. It provides the broadest possible US equity exposure.
Best for: Investors wanting maximum diversification with a "set and forget" approach to US equity investing.
Key characteristics: Maximum diversification, includes all market caps, very similar to S&P 500 (large-caps dominate), lowest expense ratios available.
Which Index Should You Choose?
Choose S&P 500 (SPY/VOO) if you want:
- • The most common benchmark for comparison
- • Broad large-cap exposure across all sectors
- • A long track record (since 1957)
Choose NASDAQ 100 (QQQ) if you want:
- • Heavy exposure to technology and growth
- • Higher risk/reward potential
- • Belief in tech sector outperformance
Choose Dow Jones (DIA) if you want:
- • Exposure to established blue-chip leaders
- • Lower volatility than broader indices
- • Dividend-focused investing
Choose Russell 2000 (IWM) if you want:
- • Small-cap exposure for diversification
- • Potential outperformance in expansions
- • More domestic-focused companies
Choose Total Market (VTI) if you want:
- • Maximum diversification in one fund
- • Exposure to large, mid, and small caps
- • The simplest "own everything" approach
- • The lowest possible expense ratios
Frequently Asked Questions
What are the major US stock market indices?
The five major US indices are the S&P 500 (500 large-cap stocks), NASDAQ 100 (100 tech-heavy growth stocks), Dow Jones Industrial Average (30 blue-chip stocks), Russell 2000 (2,000 small-cap stocks), and the Total US Stock Market (4,000+ stocks). Each tracks a different segment of the market and serves different investment goals.
Which US stock index is best to invest in?
It depends on your goals. The S&P 500 or Total Market (VTI) are best for broad, low-cost exposure to US equities. The NASDAQ 100 suits investors bullish on tech with higher risk tolerance. The Dow Jones offers blue-chip stability and dividends. The Russell 2000 provides small-cap growth potential. Most investors do well with just the S&P 500 or Total Market.
What is the difference between S&P 500, NASDAQ, and Dow Jones?
The S&P 500 tracks 500 large-cap companies across all sectors and is market-cap weighted. The NASDAQ 100 holds 100 large non-financial companies (about 50% tech). The Dow Jones has only 30 blue-chip stocks and uses price-weighting instead of market-cap weighting, making it less representative but still widely followed.
How many stocks are in each US index?
S&P 500: ~500 stocks, NASDAQ 100: 100 stocks, Dow Jones: 30 stocks, Russell 2000: ~2,000 stocks, Total Market (VTI): 4,000+ stocks. Despite the size differences, the S&P 500 and Total Market perform very similarly because large-caps dominate both by market capitalization.