What is an Asset Class?
An asset class groups investments with similar characteristics and behavior. The major asset classes are equities (stocks), fixed income (bonds), cash and equivalents, real estate, and commodities. From 1926 to 2023, US large-cap stocks returned approximately 10.3% annually, long-term government bonds about 5.5%, and Treasury bills around 3.3%. Each asset class carries distinct risk-return characteristics and responds differently to economic conditions.
Correlation Between Asset Classes
The value of diversification comes from low or negative correlations between asset classes. Stocks and bonds have historically had a correlation of roughly 0.0 to -0.3, meaning they often move in opposite directions. When stocks fell 37% in 2008, long-term Treasury bonds gained 26%. Commodities have near-zero correlation with both stocks and bonds. Real estate (REITs) correlates moderately with stocks at about 0.5-0.6. Combining uncorrelated assets reduces portfolio volatility without proportionally reducing returns.
Key Considerations
Within each asset class, sub-categories offer further diversification. Equities divide into domestic and international, large-cap and small-cap, growth and value. Bonds split into government, corporate, and municipal, with varying durations and credit qualities. Alternative asset classes like private equity, hedge funds, and cryptocurrency have gained attention but carry higher fees and complexity. Most investors can build a well-diversified portfolio using just 3-5 low-cost index funds covering the major asset classes.