Robert E. Wright is the Nef Family Chair of Political Economy at Augustana College in South Dakota and the author of numerous books, including, with David Cowen, “Financial Founding Fathers: The Men Who Made America Rich.”

The recent announcement that Wall Street’s most iconic institution, the New York Stock Exchange, would be acquired by Atlanta-based IntercontinentalExchange Inc. (ICE) seemed weighted with symbolism.

For one thing, it represented another marker in the decline of New York City as the center of global finance. It also suggested that the world of trading and exchanges was entering a uniquely modern age of technology-driven consolidation. You may recall, for example, the mergers that the NYSE conducted with Archipelago Holdings Inc. (2006), Euronext NV (2007) and the American Stock Exchange (2008).

Since the NYSE (then called the Stock and Exchange Board) first merged with another exchange shortly after the Civil War, its history has always been characterized by competition and consolidation. It suggests that financial exchanges respond to evolving economic conditions like any other industry, and that bigger often isn’t better....