The pink line here is the efficient portfolio frontier when we have only stocks and bonds to invest.

这条粉色曲线就是有效边界,这个投资组合只包括了股票和债券。

耶鲁公开课 - 金融市场课程节选

Irving Fisher also drew on the curve a production possibility frontier for society, which he made downward-curved.

欧文·费雪还画了一条曲线,代表了社会的生产可能性边界PPF,这是一条向下的曲线

耶鲁公开课 - 金融市场课程节选