In its latest look at mobile ad revenues, eMarketer estimates Google is generating nearly one-fifth of its US advertising revenues from mobile search, coming in at 19.1%.

In yet another indication of how fast the mobile ad market is growing, only two years ago mobile made up just 4.8 percent of Google’s US ad revenues. By 2015 mobile is expected to account for just over 30 percent of Google’s ad revenues in the US. Desktop search revenue share is predicted to fall below 50 percent in that time.

emaketer google mobile ad shareIt’s worth noting that eMarketer counts tablets in its mobile numbers. Google, however, has started grouping tablets with desktop, not smartphones. Google AdWords enhanced campaigns, which went into full effect in July, lump tablet and desktop bidding together so all desktop campaigns automatically include tablet bidding. eMarketer has not indicated whether enhanced campaigns are contributing to Google’s projected mobile revenue increases.

While Google’s mobile display revenue share is expected to grow at a faster rate than mobile search (147 percent vs. 61 percent) by 2015, mobile search will continue to dominate Google’s share of mobile ad revenues. YouTube is the main driver for the increase in Google’s mobile display revenue according to eMarketer.

Overall 22.9 percent of Google’s US ad revenues will come from mobile channels.

For more on the latest mobile ad revenue estimates, including Facebook and Yahoo’s numbers, see our post on Marketing Land Forecast: Mobile To Be 48 Percent Of Display Revenue By 2017