The PE ratio (Price / Earnings ratio) is the price of a stock or stock market index divided by past or future earnings (PE ratio = Price / Earnings). For example, if the price of a stock is $20 per share and that particular company earned $2 per share over the past 12 months, then the trailing twelve month PE ratio would be $20 / $2 or 10.
Many investors use the PE ratio to determine if a stock or the stock market as a whole is expensive or not. For example, the average PE ratio for the S&P 500 index from 1950-2000 was 15.4. When the market peaked in early 2000 the PE ratio of the S&P 500 was a relatively high 30 suggesting that stocks were expensive.
Related Terms: Earnings – Forward Earnings – Earnings Yield – Dividend – Dividend Yield