Volatility
Volatility measures how much an investment's price fluctuates over time. High volatility means large, unpredictable price swings; low volatility means stable prices. Standard deviation is the most common volatility measure; the VIX index measures expected S&P 500 volatility.
Volatility is often proxied by standard deviation of returns. The S&P 500's annual standard deviation has historically been about 15–20%, meaning returns in most years fall within ~30–40 percentage points of the average.
Volatility ≠ risk for long-term investors. A volatile asset that always recovers is not risky over a 20-year horizon. True risk is permanent loss of capital. Short-term investors face genuine risk from volatility because they may be forced to sell during a drawdown.
Higher volatility assets (small-cap stocks, emerging markets, cryptocurrency) historically provide higher long-run returns as compensation for enduring price swings — this is the equity risk premium. Lower-volatility assets (bonds, money market funds) are suitable for money you need within 1–3 years.
Related terms
- Bear Market
- A bear market is a prolonged decline in asset prices — commonly defined as a 20% or greater fall from a recent peak, sustained for at least two months. Bear markets are associated with recessions, declining corporate earnings, or systemic financial stress.
- Diversification
- Diversification is the practice of spreading investments across different assets, sectors, or geographies to reduce risk. A diversified portfolio is less volatile than any single holding because losses in one area are offset by gains in others.
- Portfolio Rebalancing
- Rebalancing is the process of realigning the weights of portfolio holdings back to a target asset allocation — selling assets that have grown above target and buying those that have fallen below.
- Asset Allocation
- Asset allocation is the percentage split of a portfolio among different asset classes — typically stocks, bonds, and cash. It is the primary driver of long-term portfolio risk and return.