since all the information is in the current price, you don't have to worry about whether it went up or down yesterday, to decide what it's going to do today.

因为当前价格代表了所有信息，你就不需要去考虑昨天股价,是涨了还是跌了，再去判断它今天的价格会怎么变化。

麻省理工公开课 - 计算机科学及编程导论课程节选