During the 1990s, the United States underwent a dramatic transformation: investing in stocks, once the province of a privileged elite, became a mass activity involving more than half of Americans. Pop Finance follows the trajectory of this new market populism via the rise of investment clubs, through which millions of people across the socioeconomic spectrum became investors for the first time. As sociologist Brooke Harrington shows, these new investors pour billions of dollars annually into the U.S. stock market and hold significant positions in some of the nation's largest firms. Drawing upon Harrington's long-term observation of investment clubs, along with in-depth interviews and extensive survey data, Pop Finance is the first book to examine the origins and impact of this mass engagement in investing.