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In finance, the Sharpe ratio (also known as the Sharpe index, the Sharpe measure, and the reward-to-variability ratio) is a way to examine the performance of an investment by adjusting for its risk. The ratio measures the excess return (or risk premium) per unit of deviation in an investment asset or a trading strategy, typically referred to as risk (and is a deviation risk measure), named after William F. Sharpe.〔 ==Definition== Since its revision by the original author, William Sharpe, in 1994, the ''ex-ante'' Sharpe ratio is defined as: : where is the asset return, is the return on a benchmark asset, such as the risk free rate of return or an index such as the S&P 500. is the expected value of the excess of the asset return over the benchmark return, and is the standard deviation of this excess return. This is often confused with the information ratio, in part because the newer definition of the Sharpe ratio matches the definition of information ratio ''within the field of finance''. Outside of this field, information ratio is simply mean over the standard deviation of a series of measurements. The ''ex-post'' Sharpe ratio uses the same equation as the one above but with realized returns of the asset and benchmark rather than expected returns - see the second example below. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sharpe ratio」の詳細全文を読む スポンサード リンク
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