• by Laurie Sullivan , Staff Writer @lauriesullivan, September 8, 2015

Data released Tuesday forecasts that Google will get $2 of every $5 marketers spend in 2015 on digital advertising in the United States.

By 2017, Google's U.S. net digital ad revenue share will rise to 13.1%, up from 12.7% in 2015. Facebook's share will rise to 5.9% from 4.2%, respectively. Microsoft also will gain slightly -- reaching 1.6%, up from 1.4%, respectively. eMarketer's forecast estimates Yahoo will lose share, dropping to 1.3% in 2017, from 1.4% in 2015. 

Overall, marketers will spend $204.14 billion in 2017 on digital advertising in the U.S., up from $183.66 billion in 2015.

Google will earn the majority of its advertising revenue from search. eMarketer forecasts Google's search advertising revenue to reach $19.21 billion in 2015, or 72.4% of net U.S. search ad revenue. About 36.6% of Google's U.S. digital advertising revenue comes from search, or some 36.6%.

Google will hold about 32.9% of mobile ad revenue in the U.S. -- or nearly $10.02 billion -- in 2015, rising to a bit more than $16 billion by 2017. Facebook follows with 19.4%, or nearly $5.9 billion, rising to $10.3 billion in 2017. 

In the U.S., Google's dominance directly relates to its search ad presence. In 2015, search is still the major ad format for Google. The company will capture more than 72% market share, according to eMarketer analyst Monica Peart. Also, the company alone represents nearly one-third of net mobile ad revenue. No single company comes close to commanding that level of market share.

Microsoft continues to gain market share with its search engine Bing, but lags when it comes to gaining U.S. mobile market share. The company doesn't make eMarketer's list of top eight companies when it comes to U.S. mobile ad revenue.

Twitter ranks No. 3, earning nearly $1.2 billion in 2015 -- rising to $2.2 billion in 2017. Yahoo at No. 4 takes $885 million, rising to $1.2 billion. Apple comes in at No. 5 -- taking $795 million and rising to $1.4 billion. Pandora at No. 6 with $737 million and $1.2 billion; YP ranks No. 7 with $637 million and nearly $896 million; and Yelp comees in at No. 8 with $212 million and $377 million, respectively.