The numbers are slightly ahead of eMarketer's projections from last year. The upward revision is due largely to the unexpected growth rate of mobile advertising spending.
The new numbers suggest mobile advertising will generate $8.51 billion in 2013, almost double of last year's $4.36 billion. This year, mobile will account for about a fifth of digital advertising dollars, and 5% of all media advertising revenues.
Mobile's share of total media advertising is forecast to triple (to 15.8%) by 2017.
Source - Mobile Pushes US Digital Ad Market Higher, Promax/BDA