eMarketer estimates that US advertisers will increase mobile search ad spending 80.6% this year to $3.54 billion, up from $1.99 billion in 2012. US digital search ad spending including mobile will also rise, from $17.58 billion in 2012 to $19.76 billion in 2013. This represents a comparatively restrained growth rate of 12.4% driven largely by increased mobile search spending. And the spending gap between mobile and desktop paid search will narrow even further over time: eMarketer projects that by 2016, advertisers will spend $24.45 billion on search, with $10.3 billion of that going toward mobile. Read the rest at eMarketer.