<Li> Six utilities (EDF Energy, Centrica, RWE npower, E. on, Scottish Power and Scottish and Southern Energy) share 95% of the retail electricity market . </Li> <Li> Four mobile phone networks . Phantom networks like Tesco Mobile have attempted to free the market, but there are still just four core signal providers in EE, Vodafone, O2 and 3 Mobile . </Li> <Li> Big Four Accounting Firms - (KPMG, PWC, Ernst and Young and Deloitte) These four firms audit 99% of the companies in the FTSE100 and 96% of the companies in the FTSE 250 Index . </Li> <Ul> <Li> Six movie studios (Walt Disney Pictures, Sony Pictures, Universal Pictures, 20th Century Fox, Paramount Pictures, Warner Bros. Entertainment) receive almost 87% of American film revenues . </Li> <Li> The television and high speed internet industry is mostly an oligopoly of seven companies: The Walt Disney Company, CBS Corporation, Viacom, Comcast, Hearst Corporation, Time Warner, and News Corporation (now 21st Century Fox and News Corp). See Concentration of media ownership . </Li> <Li> In March 2012, the United States Department of Justice announced that it would sue six major publishers for price fixing in the sale of electronic books . The accused publishers are Apple, Simon & Schuster Inc, Hachette Book Group, Penguin Group, Macmillan, and HarperCollins Publishers . </Li> </Ul>

Which one of the following explains why so few firms are global