John C. Bogle

As Vanguard's chairman, Bogle used the annual report letters to make one argument over and over, that costs eat returns, and to criticise his own industry's fees while doing it. Because Vanguard is owned by its funds, his letters spoke to investors as the owners, and the consistency is striking: what he wrote in the 1970s about index funds is what he was still writing decades later, and the evidence moved his way.