Jack Bogle: The Vanguard 500 Index Fund Admiral Shares (VFIAX) is a low-cost way to gain diversified exposure to the U.S. equity market. The fund offers exposure to 500 of the largest U.S. companies, which span many different industries and account for about three-fourths of the U.S. stock market’s value. It has a 0.04% expense ratio and its performance in the long term has beaten many active funds over the years.