As user focus shifts from the desktop to mobile, it appears as though mobile ad revenue is as well. The latest data from eMarketer says mobile ad spending jumped significantly in 2013 and that while Google still holds the biggest percentage, Facebook is quickly increasing its share.

Last year mobile spending jumped 105% to almost $18 billion, and eMarketer is predicting another 75% bump next year to $31.5 billion. It is also said that mobile ads will represent nearly 25% of the overall mobile spend in 2014.

Google is still taking in the most, commanding a 49.3% share of mobile ad revenue last year, but that number is a slight decrease from the year prior and is expected to fall once again this year.

Facebook, on the other hand, jumped significantly from a 5.4% share in 2012 to 17.5% last year. The company is expected to continue its growth in the mobile ad share department even further in 2014 to 21.7%, according to eMarketer.

Mobile only made up about 11% of Facebook's total ad grab in 2012, before it jumped to nearly half in 2013, and it is said that it could reach as high as 63% this year. At 53% of the company's total ad revenue last quarter, it was the first time it made more from mobile than it did from desktop ads.

After the top two, Twitter jumped from 1.5% in 2012, to 2.4% the following year, and is expected to rise marginally to 2.6% this year. Pandora will capture around a 1.7% share in 2014, according to eMarketer's data.

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