Omnicom Group will acquire Interpublic Group in a deal that will create the world’s largest advertising business, the companies confirmed Monday.A combined entity would have net revenue of more than $20 billion,

Omnicom is buying Interpublic Group in a stock-for-stock deal that will create an advertising powerhouse with combined annual revenue of almost $26 billion. The New York City agencies have had a hand in iconic marketing campaigns like “Got Milk” for the California Milk Processor Board,