ZenithOptimedia defines media revenue as all revenue deriving from businesses that support advertising, to determine which companies are most important for the marketing industry.

The rise of mobile devices has meant Google has become a central search function for people on the move which has created new opportunities for Google to target them with display ads.

However another beneficiary of the increasing mobility of people has been Facebook, the fastest growing of the top 30 media owners. Facebook’s media revenues grew 63% over the past year and it is now the 10^th-largest media owner in ZenithOptimedia’s ranking.

Elsewhere Baidu – China’s equivalent of Google – grew 43% over the year making it the world’s 14^th-largest media owner, ahead of digital rivals Yahoo! ( 18^th) and Microsoft ( 21^st).

There are five purely digital media owners in the top 30 – Google, Facebook, Baidu, Yahoo! and Microsoft. Between them they generated $71bn in media revenue, which represents 68% of all global digital adspend.

Jonathan Barnard, ZenithOptimedia’s head of forecasting said: “The top digital media owners currently maintain a strong grip on the digital ad market, but they face the constant threat of displacement by disruptive innovators. While some emerging-market media owners face challenges in expanding their businesses in the short term, we expect to see more media owners from emerging markets enter the top 30 over the next few years.”