With the government expected return, we want to make that expected return as a fourth asset-- rf we could call it r4 but I'll call it rf-- it's a special asset.

根据政府的期望收益率，我们将其作为第四种资产-,可以称之为r4，我们写成-,这是个特殊的资产。

耶鲁公开课 - 金融市场课程节选