Omnicom Group Inc. announced two important senior management changes at the holding company and network level. Effective immediately, Daryl Simm moves into the role of President and Chief Operating Officer of Omnicom Group, a newly created position. Simm has served as Chief Executive Officer of Omnicom Media Group (OMG) for more than two decades, having joined Omnicom in 1998. In his new role at the holding company, Simm will work directly with Chairman and CEO John Wren to oversee business operations across Omnicom.