Advertising agency group WPP has seen its market capitalization fall $2.6 billion after it reported flat results Thursday. WPP's shares were down almost 13 percent and the firm's chief executive, Martin Sorrell, said there were several reasons for the lack of revenue growth. "The major factors influencing this performance were probably the long-term impact of technological disruption and more the short-term focus of zero-based budgeters, activist investors and private equity than, we believe, the suggested disintermediation of agencies by Google and Facebook or digital competition from consultants," he said in an online statement.