Omnicom Group Inc. is an American global media, marketing and corporate communications holding company, headquartered in New York City. It was founded in 1986.
Omnicom's branded networks and specialty firms provide services in four disciplines: advertising, customer relationship management (CRM), public relations and specialty services.
The services included in these disciplines are media planning and buying, digital and interactive marketing, sports and events marketing, field marketing and brand consultancy.
Omnicom Group was ranked as one of the four largest advertising agencies in the world by The New York Times in 2002. In 2014, Omnicom was considered the second largest advertising holding company by The Wall Street Journal. The company employs more than 77,000 employees in over 100 countries worldwide.
According to en.wikipedia