在书上看到说：assets whose returns covary positively with consumption make consumption more volatile, and so must promise higher expected returns to induce investors to hold them.
请问一下，消费与收益的协变到底如何决定资产的风险性的呢？以上这段话是说明资产风险高吗？
可是我们老师的讲义上却用的stochastic discount fator和return之间的关系解释的资产的风险高低，请问SDF和return又是如何决定风险的呢？
谢谢各位，急等答复~~~~