Beta and Volatility (VIX)
— a Guide to Risk-Measurement Metrics
Beta measures an individual stock's sensitivity to the market, and VIX measures the market's overall fear and volatility. Understand both and you can manage portfolio risk quantitatively.
What Is Beta?
Beta shows how sensitively an individual stock moves relative to the S&P 500 (the market), which is set at a baseline of 1.0. A beta of 1.5 tends to mean roughly +15% when the market is +10%, and roughly -15% when the market is -10%. A beta of 0.5 is a defensive stock that moves at about half the market's level.
High Beta vs. Low Beta
- High beta (Beta > 1.5) — growth stocks, tech stocks, biotech, and so on. Outperformance in a bull market, outsized losses in a bear market.
- Near a beta of 1.0 — moves similarly to the market. A large index-tracking ETF, for example.
- Low beta (Beta < 0.7) — utilities, consumer staples, healthcare. A defensive character, relatively strong in a bear market.
- Negative beta — gold, some bonds. These tend to move in the opposite direction from the market.
Reading the VIX (Volatility Index)
The VIX (CBOE Volatility Index) is an expected-volatility index for the next 30 days, computed from S&P 500 options prices. It's commonly called the "fear index."
- VIX 20 or below — a stable market. Investors are at ease.
- VIX 20–30 — rising uncertainty. A watch zone.
- VIX 30 or above — a fearful state. Volatility is widening.
- VIX 40 or above — extreme fear. Historically, this range has often been a mid- to long-term buying opportunity.
Beta and Rebalancing
When the VIX spikes, high-beta stocks tend to lose more than the market. In that kind of environment, using rebalancing to raise your allocation to low-beta assets can reduce your portfolio's overall volatility. Sector rotation is another way to manage beta.