刚看了一点Granger和Morgenstern的Predictability of stock market prices, 随机游走模型，说的是过去的价格不能预测未来的价格变化，但并没有说除价格以外的其他信息，比如size,turnover,p/e ratio, EBITDA等，不能预测价格。EMH说的是价格包含的信息，所以EMH成立但RWH不一定成立。这么理解对吗？

但是EMH里weak form efficiency说cannot use past price to predicte future price,这不是和RMH一样吗，那RMH成立，不是只能推导weak form efficiency成立吗，怎么RHW成立，EMH一定成立呢？

if fundamental changes in economic conditions cause expected returns to vary through time (e.g., due to business cycle fluctuations), then stock returns should contain a predictable component to reflect the time-varying risks associated with those fundamental changes. In such an environment, the EMH requires that stock returns be predictable, i.e., a non-random walk, so if they are random, that would be inefficient because it would not properly reflect changes in the underlying fundamentals."

EMH成立，RWH不成立我是明白了。但是RWH成立，EMH一定成立还是不明白。。。