Beta

Before you rely on it

What to check

Look at the benchmark and the window. The same fund shows different betas against a broad index and against its own sector.

The common error

Where people go wrong with beta

Reading a low beta as safe. A fund can have almost no relationship to the index and still be enormously volatile on its own, because beta measures how it moves with the market, not how much it moves.

Worked through

Beta in plain numbers

A stock has a beta of 1.3 against a broad market index. If the market rises 8% in a year, the stock is expected to rise about 10.4%, all else equal. If the market falls 10%, the stock is expected to fall about 13%, and a utility with a beta of 0.6 would move 4.8% in the first case and 6% in the second. Real stocks do not follow these numbers exactly. Beta is estimated from past returns, and the fit is usually loose; a stock can post a poor year in a rising market for reasons that have nothing to do with the index.

Easily confused

Beta and its neighbours

Beta measures sensitivity to a market. It is not volatility, and it is not risk in general. Volatility, usually standard deviation, measures how much returns move around their own average, including moves that have nothing to do with the market; a stock can have a low beta and be very volatile if its swings are unrelated to the index. Beta is also different from alpha, which describes return beyond what beta would predict. Two funds with the same beta can have different total risk, so one number cannot tell the whole story.

In real decisions

Where beta turns up

Analysts use beta in the capital asset pricing model to estimate the return an investment should earn for the market risk it carries. Portfolio managers use it to gauge how a portfolio might move if the market does. Someone wanting less market exposure might add low-beta holdings; companies use beta when estimating their cost of equity. Fund fact sheets often print it beside standard deviation, so a reader can see both the tie to the market and the total movement in one view.

Know the edges

Where beta stops being reliable

Beta depends on the index chosen, the time window and the frequency of returns, so the same stock can show different betas in different sources; it is backward-looking and can change as a company changes. It assumes a linear relationship that often breaks in extreme markets. Betas near one are common and say little. A low beta does not guarantee protection in a crash, and treat it as one descriptive statistic and use it alongside the rest of the picture.

Quick answers

What people ask about beta

Can beta be negative? Yes, though it is rare. A negative beta means an asset tends to move opposite to the market. Some gold-related investments and certain hedging instruments have shown it at times. It is not stable.

Is a low-beta stock safe? Not necessarily. Low beta means less sensitivity to the market, but the company can still fall for reasons of its own. Use beta with other risk measures.