When it comes to major U.S. industries, three tends to be the magic number. Historically, auto manufacturing was long dominated by Chrysler, Ford and General Motors – the so-called “Big Three,” which at one point controlled over 60% of the U.S. auto market. A dominant trio shows up elsewhere, too, in everything from the U.S. defense market – think Lockheed Martin, Boeing and Northrup Grumman – to cellphone service providers (AT&T, T-Mobile and Verizon).