NEW YORK: Mobile advertising expenditure in the US is expected to almost double in 2013 as revised figures from media research firm eMarketer indicate spending of $8.51bn for the year.

This represents an 11% increase on eMarketer's previous, June, forecast of $7.65 billion for 2013. It now predicts mobile spending will rise 95% this year to account for 20.1% of digital ad spending and 5.0% of total media adspend.

Growth will slow in subsequent years but remain in double-digits out to 2017, by when mobile is expected to be valued at $31.13bn. This is equivalent to a 50.7% share of digital ad spending and a 15.8% share of all media ad spending.

eMarketer bases its estimates on the analysis of reported revenues from major ad-selling companies; data from the Interactive Advertising Bureau and PricewaterhouseCoopers; estimates from other research firms; consumer internet usage trends; and eMarketer interviews with executives.

In terms of format, eMarketer said the shift of search from desktop to mobile would continue. From a 2.1% share of digital search spending in 2010, mobile search is forecast to take 22.1% in 2013 and 59.6% in 2017.

A similar, if slower, pattern is evident in display spending. Some 21.7% of all digital display ad spending is expected to be on mobile in 2013, rising to 48.4% by 2017.

Within that classification, video will be the fastest-growing mobile ad format, rising from a value of $576m in 2013 to $2,987m in 2017, an increase of 418%. And mobile's share of the digital video format will rise more than double from 14% to 32.5%.

Within mobile alone, search continues to be the most popular format, with 51.5% of all spending on mobile ads being directed here. Display, including banners, video and other formats, takes 44.8%. Other formats such as SMS and email make up the remainder.

And while mobile display is growing faster than search it will still only take a 46.6% share by 2017, compared to search's 49%.

Data sourced from eMarketer; additional content by Warc staff