New York—Mobile ad spending is driving most of the growth in overall digital ad spending, while spending on ads aimed at laptop and desktop users has slowed, according to a report by eMarketer. eMarketer projects that U.S. mobile advertising spending, including classified, video, banners and other rich media, will reach $9.6 billion by the end of this year, up 120.0% from the $4.4 billion spent in 2012. Spending on ads served to desktops and laptops is expected to grow just 1.7% to $33.0 billion, down from 6.6% growth last year. The report forecasts that digital ad spending on mobile devices will overtake laptop-desktop campaigns by 2017. By then, mobile ad campaign spending will hit $35.6 billion, compared with $27.2 billion spent on desktop programs.