Marks explains the strong form of efficient market hypothesis claims you cannot beat the market.
“the efficient market hypothesis posits that because of the concerted action of investors, prices converge with fair value, everything is priced right, and you can't beat the market.”
Marks argues that if risky investments guaranteed higher returns, they would not be risky by definition.
“if riskier investments could be counted on to produce higher returns, then by definition, they're not risky. So that can't be right.”