Most people have little trouble ticking off the names of the big stock exchanges in New York, London and the major cities of Europe and Asia. But if regulators say “yes,” two less familiar exchanges in Chicago will combine to become the world’s largest. In mid-October, the Chicago Board of Trade agreed to be purchased by the Chicago Mercantile Exchange for about $8 billion, topping a wave of exchange mergers in the U.S. and Europe. Two factors drove the deal, according to Wharton professors: the enormous growth in the use of futures, options and other derivatives to hedge risks and speculate, and the need for economies of scale to compete with exchanges that have grown through mergers. Indeed, the business of executing investors’ buy and sell orders is changing rapidly, as markets go global and harness lightning-fast computers and communication technology. On Oct.…