MENLO PARK, CA: More than one in five (22%) mobile ad campaigns in the US directed consumers to rich media such as a video or an app during August 2010, data from Millennial Media have shown.

According to the new report, the remaining 78% of the campaigns opened out onto a landing page or a website.

In all, 43% of US mobile campaigns were targeted in some way, with the remainder sent to a general audience.

Around half of targeted campaigns employed location-based targeting, reflecting the popularity of social networks such as Foursquare, members of which "check in" to bars and shops via the GPS features in their smartphones.

Millennial Media found that restaurants, retail franchises and small businesses are most likely to conduct a location-based campaign.

"Targeted-audience methods allow advertisers to engage in a deeper dialog with mobile users and the result is stronger campaign interaction rates," it added.

The study also suggested that 30% of mobile subscribers who accessed retail content on their phone do not respond to PC-based online campaigns and in-store marketing.

"For advertisers this means there is a new retail audience that can only be reached through mobile," Millennial Media added.

"To reach this untapped market, it is imperative that brands double down with mobile this holiday season."

More generally, the report found the size of the mobile web increased from 78.7 million to 80 million users during August.

The typical user views 122 pages per month, with an average session time of four minutes and 46 seconds.

Data sourced from Millennial Media; additional content by Warc staff