Adjusting MV-efficient portfolio frontier bias for skewed and non-mesokurtic returns

• We investigate bias adjustment for mean–variance efficient portfolio frontiers.
• Portfolio frontier bias comes from the estimation error of mean and variance.
• We examine which portfolio frontiers are closed to the actual frontier.
• The Portfolio frontier bias is related to return skewness and kurtosis.
• We propose revised portfolio frontiers which perform more desirable.

This study investigates the bias adjustment for mean–variance efficient portfolio frontiers due to population mean and variance estimation error in Taiwan stock market. Although Siegel and Woodgate (2007; Management Science, 53, 1005–1015) and Kan and Smith (2008; Management Science, 54, 1364–1380) suggested two portfolio frontiers that improved upon the out-of-sample performance of a traditional sample portfolio frontier. However, this study shows that, using the copula function and Gram-Charlier series, the two frontiers are theoretically biased toward the actual frontier unless returns behave normally, and the bias is related to the return skewness and kurtosis. Indeed, the two frontiers are empirically biased to the lower-left side of the actual ones, because the Taiwan stock returns are right-skewed and highly leptokurtic. Thus, this study thus proposes revised portfolio frontiers that are closer to the actual frontier than unrevised ones. This improvement may enhance the estimation accuracy of the capital market line, and hence this study can provide an effective investment reference.