A history of how the idea of indexing originated and evolved into the multi-trillion-dollar exchange-traded funds (ETF) industry. The book details the key people and institutions, including John Bogle, Larry Fink, Wells Fargo, State Street, and S&P, and the roles they played in turning indexing from a radical idea into one of the most important innovations in modern finance. It also explores the unintended consequences of trillions of dollars flowing into passive investing, including the growing influence of the small committees that decide which companies are included in major indexes.