How stocks are traded in the United States has been totally transformed. Gone are the dealers on NASDAQ and the specialists at the NYSE. Instead, a company's stock can now be traded on up to sixty competing venues where a computer matches incoming orders. A majority of quotes are now posted by...

Is something wrong with the structure of the U.S. stock market? Both industry participants and scholars have recently faulted the equity market for its lack of innovation. In particular, they have emphasized that stock exchanges may not have the right incentives to provide innovative solutions...