One question that comes up is that maybe-- this is for the U.S. data-- and some people say, well, maybe, why are we looking at the U.S.?

这又产生了一个新问题,这是采用美国市场的数据得出的结果,有些人会问,为什么光研究美国市场呢

耶鲁公开课 - 金融市场课程节选

They might say my sample period was off, ... but that's what the theory-- ... using my data for the sample period that I computed-- the expected returns and co-variances says one should do.

他们可能说我的采样周期是有问题的，不过我的结果都是靠理论-,我采用自己收集的数据计算出-,预期收益和协方差可以用来指导我们的投资行为。

耶鲁公开课 - 金融市场课程节选