Volatility

The degree of variation in a security's price over time; higher means bigger swings.

Volatility is a statistical measure of the dispersion of returns for a given security or market index. In simpler terms, it represents how much and how quickly a stock's price swings up and down over a specific period. A highly volatile stock experiences rapid, dramatic price movements, while a low-volatility stock tends to have steadier, more gradual price changes. Investors typically observe volatility in two ways: historical volatility, which measures past price fluctuations, and implied volatility, which is derived from options pricing and reflects the market's expectation of future price swings. It is commonly calculated using the standard deviation of a security's daily price returns over a set timeframe, such as 30 or 90 days. Understanding volatility is crucial for retail investors because it directly relates to risk. High volatility means greater potential for both rapid gains and sudden, significant losses. Investors use volatility to size their positions, set stop-loss orders, and assess whether a security aligns with their personal risk tolerance. A common pitfall is equating high volatility with a bad investment; in reality, volatility simply measures price movement, and some investors actively seek it out to capture short-term trading profits.

If Stock A has an average annual return of 8% with a standard deviation (volatility) of 15%, statistical theory suggests that about 68% of the time, its annual return will fall within one standard deviation of the mean. This means its return in any given year is highly likely to be between -7% (8% minus 15%) and +23% (8% plus 15%).