Beta (portfolio)

Beta quantifies the systematic risk of a portfolio or single security by regressing its returns against a market benchmark, usually the S&P 500. A beta of 1.2 means the security has historically risen or fallen 12% for every 10% market move. Technology stocks and growth indexes typically exhibit betas of 1.1 to 1.4, while utilities and consumer staples sit below 1.0. Beta measures relative volatility, not risk of permanent loss.

Example: a tech employee’s concentrated portfolio has a 1.6 beta driven by employer stock and growth ETFs. In a 10% market decline, the portfolio should fall roughly 16%. Diversifying 30% into bonds (beta near 0) and 20% into dividend stocks (beta 0.8) brings portfolio beta to about 1.0, aligning risk with the broad market.

Common mistake: treating low beta as low risk for a retiree. A 0.6 beta bond-heavy portfolio can still lose 20% in a rising-rate environment (as 2022 demonstrated), because beta measures market correlation, not interest-rate or credit risk.

Portfolio beta matters at asset allocation reviews, at concentrated stock hedging decisions, and when comparing portfolios with different equity exposures.