You want to, for any given expected return, you want to minimize the standard deviation, so it's the left-most line and that means that everyone will be holding the same portfolio.

你希望，在期望收益固定的情况下，你肯定希望将标准差最小化，而这条线是最左边的线,这就意味着所有人,都愿意持有这样的投资组合。

耶鲁公开课 - 金融市场课程节选