Yahoo's ad business in five ever smaller numbers Yahoo has lost its chief operating officer who was in charge of steering the internet company's advertising business, as it continues to lose share in the digital ad market. Henrique de Castro is leaving swiftly after reports he fell out with Marissa Mayer, who poached him from her former home Google as part of her turnaround plan for the purple-plastered company. Mr de Castro's success at Google, where much depends on its magic algorithms, did not translate well to Yahoo's business which relies more on building relationships with brand advertisers, one analyst said. Here are five statistics from research firm E-Marketer which show that while Yahoo's share price has soared and Ms Mayer has transformed perceptions of the company, its advertising figures are still under-performing the market. Yahoo's global advertising revenues are falling, down 2.2 per cent in 2013 while Google, Facebook, Microsoft, Amazon, Pandora, Twitter, LinkedIn and mobile advertising platform Millenial Media all saw at least double digit growth. Yahoo is no longer number two to Google: It lost its spot as the second largest US digital advertising seller to Facebook in 2013, and more social competitors such as Twitter and LinkedIn are growing, albeit from a low base. In the US, the world's largest advertising market, Yahoo's share of digital advertising revenues declined to 5.8 per cent in 2013, from 6.8 per cent. Facebook grew to 7.4 per cent, while Google is still the behemoth with almost 40 per cent of the market. Yahoo's share is forecast to fall further, according to E-Marketer, to 5 per cent by 2015, with the only other fallers Microsoft, AOL and IAC, the owner of sites such as Match.com and Vimeo. Even in display advertising, traditionally Yahoo's strength, its share has more than halved since 2008. In 2013, it had 7.2 per cent of total display advertising revenues compared with Facebook's 17.9 per cent. In 2008, Facebook had just 2.9 per cent.