Efficient markets" is a theory about-- well it came in about three decades ago, maybe it's closer to four decades ago-- it's a theory that financial markets work very well and incorporate information very well.

有效市场是...,大约三十年前,甚至四十年前,有人提出了这一假说,他认为金融市场运行良好,而且信息披露全透明

耶鲁公开课 - 金融市场课程节选