Two years ago, finance executives at Cadence Design Systems Inc. had to decide whether Cadence should continue to list on the New York Stock Exchange (NYSE) and the Nasdaq or throw its full weight behind just one. James Haddad, Cadence's corporate vice president of finance, quantified differences in technology, trading speeds, cost to the company, cost of trades to the investor, reliability and confidentiality. Nasdaq, with its stealth electronic trading system, came out on top. Today, Cadence is considering giving that decision a rethink–at least if the NYSE, already the largest global exchange, gets any more global. "If the NYSE consolidates faster as far as a global footprint, we might revisit where we are listed," Haddad says. "It's our responsibility to revisit our choices periodically and make sure we are getting the same benefits."

This is hardly a concession on Haddad's part; the global nature of exchanges wasn't a factor when Cadence cut ties with the NYSE. But, the entire world of equity exchanges is being transformed–from dozens of parochial exchanges scattered around the global to a world of giants looking to grab more turf. "Everyone is is talking to everyone else," says Nelson Chai, NYSE Euronext CFO. "Ultimately, there will be just a few global exchanges."

In this evolution, bourses are consolidating, automating and converting to public companies. "The silos are breaking down," says Rajiv Shah, head of A.T. Kearney's North American Financial practice. "As cross-border alliances mature and achieve economies of scale you will see lower costs, better service, better products and better access."