Used in the context of general equities. The beta of a portfolio is the weighted sum of the individual asset betas, According to the proportions of the investments in the portfolio. E.g., if 50% of the money is in stock A with a beta of 2.00, and 50% of the money is in stock B with a beta of 1.00,the portfolio beta is 1.50. Portfolio beta describes relative volatilityof an individual securities portfolio, taken as a whole, as measured by the individual stock betas of the securities making it up. A beta of 1.05 relative to the S&P 500 implies that if the S&P's excess return increases by 10% the portfolio is expected to increase by 10.5%.
A measure of a portfolio's volatility. A beta of 1 means that the portfolio is neither more nor less volatile or risky than the wider market. A beta of more than 1 indicates greater volatility while a beta of less than 1 indicates less. Beta is an important component of the Capital Asset Pricing Model, which attempts to use volatility and risk to estimate expected returns.
The relative volatility of returns earned from holding a specific portfolio of securities. A high portfolio beta indicates securities that tend to be more volatile in their price movements than the market taken as a whole. Portfolio beta is calculated by summing the products of each security's beta times the proportional weight of the security in the portfolio. For example, if a portfolio consists of two securities, one valued at $15,000 and having a beta of 0.9 and the other valued at $10,000 and having a beta of 1.5, the portfolio beta is (0.9)( $15,000/$25,000 ) + (1.5)( $10,000/$25,000 ), or 1.14.