Share of mobile advertising revenues, %, selected companies.

Figures out today from eMarketer, a digital marketing research firm, show that Google gobbled up 31.5% of the $116.82 billion companies took in digital advertising last year. (The numbers from eMarketer are based on the total advertising revenue companies like Google earned minus the cost they have to pay affiliates for “traffic acquisition,” which is a fee paid to referrers or through programs such as Google’s AdSense.)

That’s down a little from 32% in 2011. But this year Google’s share should reach one-third of expected total advertising revenues of $116.82 billion. The next biggest winner of digital ad revenue is Facebook. Its share for 2012 was a fraction of Google’s: 4.1%.

Google is even more dominant in mobile advertising. Of the $8.8 billion companies pulled from mobile advertising, Google accounted for $4.6 billion, or 52.4%. Facebook went from a standing start—zero in 2011—to 5.4% ($470 million) in 2012. It is forecast to more than double its share to 13% ($2 billion) of this year’s $15.82 billion total.

Not taking affiliate fees into account, advertising accounted for 95% of Google’s revenues last year.