GOOGLE will sell more mobile advertising than the rest of its rivals combined for the second straight year, according to a new forecast that highlights the expansion of the Internet search leader's moneymaking prowess from personal computers to smartphones and tablets.

The report released yesterday by the research firm eMarketer projects Google Inc will generate nearly US$8.9 billion in mobile ad revenue globally this year. The figure reflects the anticipated amount that Google will retain after paying commissions to its ad partners.

The prediction sees Google with 56 percent share of the overall mobile ad market, which may hit US$16 billion this year. In 2012, Google took 52 percent, or US$4.6 billion, of the worldwide mobile ad market, said eMarketer.

Facebook Inc, the owner of the largest online social network, is expected to rank a distant second in mobile advertising this year with about US$2 billion in revenue from phones and tablets, eMarketer predicted. Although still far behind Google, Facebook has been making rapid inroads in the mobile market. Last year, Facebook sold under US$500 million in mobile advertising.

The report marks the first time that eMarketer has released digital ad numbers spanning the entire globe. The firm's previous estimates, which are closely watched in the industry, have been confined to the US ad market.

EMarketer's figures are intriguing because Google doesn't disclose how much of its total advertising revenue flows from the rapidly growing ad market. The California company has repeatedly said during quarterly discussions of its earnings that its mobile ad business is thriving.

Google's success in mobile advertising stems from its ability to establish its Internet search engine and digital maps, Gmail and the Chrome browsers, as frequently used applications on mobile devices.