In what would create the world's largest advertising company, New York-based Omnicom and Paris-based Publicis announced on Sunday that they have agreed to merge. Together the two companies accounted for $22.7 billion in total revenue last year. Initially Omnicom chief John Wren and Publicis chief Maurice LÃ©vy have agreed to serve as co-CEOs. However, LÃ©vy, 71, who had previously announced plans to step down in 2015, will become nonexecutive chairman in 30 months and Wren, 60, will take over as sole chief executive. The merger will face regulatory scrutiny in both the U.S. and France, and some analysts observed that approval is by no means assured. The advertising agencies that exist under the umbrellas of both companies represent some of the world's largest brands -- several of which compete directly against one another, including, for example, Coca-Cola and Pepsi. At a news conference to announce the merger, Wren observed that it is occurring at a time of worldwide transition from analog to digital and predicted, Everything three years from now is going to be digital. ... Everything that we do, even billboards nowadays, are digital or are becoming digital. However, The New York Times quoted David Jones of the French ad company Havas as saying that he was amazed by the industry's obsession with mergers. Clients, he said, want us to be faster, more agile, more nimble and more entrepreneurial not bigger and more bureaucratic and more complex. There is no need, he suggested, for a gigantic ad firm to service some of the new digital outlets. Instagram, he noted, has just 32 employees, but 140 million users. Facebook has 5,000 employees and 1 billion users.