[The third moment of returns is important for asset pricing, but it is hard to measure precisely, particularly at long horizons. This paper proposes a definition of the realized third moment that is computed from high-frequency returns. It provides an unbiased estimate of the true third moment of long-horizon returns, doing for the third moment what realized variance does for the second moment. The methodology is used to demonstrate that the skewness of equity index returns, far from diminishing with horizon, actually increases with horizons up to a year, and its magnitude is economically important.]

The third moment of returns is important for asset pricing, but it is hard to measure precisely, particularly at long horizons. This paper proposes a definition of the realized third moment that is computed from high-frequency returns. It provides an unbiased estimate of the true third moment of long-horizon returns, doing for the third moment what realized variance does for the second moment. The methodology is used to demonstrate that the skewness of equity index returns, far from diminishing with horizon, actually increases with horizons up to a year, and its magnitude is economically important. The Author 2012. Published by Oxford University Press on behalf of The Society for Financial Studies. All rights reserved. For Permissions, please e-mail: [email protected]. , Oxford University Press.