D avid Booth is an American billionaire investor and a pioneer in the field of quantitative and index-based investing. He is the co-founder and executive chairman of Dimensional Fund Advisors (DFA), a major global investment management firm. After studying under the Nobel laureate Eugene Fama at the University of Chicago, Booth became a proponent of the efficient-market hypothesis.

In 1981, he co-founded DFA to put these academic theories into practice, creating investment strategies based on rigorous financial science rather than traditional stock-picking. The firm became a leader in factor-based investing, building portfolios that tilt towards factors like size and value, which have been shown to produce higher long-term returns. He has grown DFA into a massive asset manager with hundreds of billions of dollars under management. In 2008, he made a historic $300 million donation to his alma mater, the University of Chicago's business school, which was renamed the Booth School of Business in his honor.