The Efficient Frontier: A Note on the Curious Difference between Variance and Standard Deviation
探讨了马科维茨有效前沿在均值-方差空间与均值-标准差空间中的几何差异，解释了资本配置线为何在一种空间中是直线而在另一种中是曲线，对理解投资组合优化有参考价值。
The Markowitz frontier of optimal portfolios is valid in both mean–variance space and in mean–standard deviation space. There are, however, some curious differences because lines in one space become curves in the other. This article explores and explains the curiosity. <b>Key Findings</b> ▪ The capital allocation line is a curve in mean–variance space. ▪ There is a line in mean–variance space that connects the riskless rate with the tangency portfolio, but it is not a capital allocation line. ▪ Volatility can be either standard deviation or variance, but their efficient frontier geometry is curiously different.