• by Mark Walsh  @markfwal, September 2, 2009

The U.S. mobile video audience hit 15 million in the second quarter, up 70% from the year-earlier period, according to the latest Nielsen "Three Screen Report." That's still only about 5% of the 270 million U.S. cell phone subscribers and 10% of subscribers with video-capable phones. Still, it's not an insignificant number of viewers.

Perhaps more intriguing to advertisers is the particular devotion of this audience, which continued to spend more time on average watching video per month via mobile than did people on the Internet (3 hours, 15 minutes versus 3:11). It should be noted, however, that this gap is closing fast-a year ago, monthly video viewing online averaged 2:12 compared to 3:37 for mobile.

And when it comes to time in front of the tiny screen, the real audience here is teenagers. They spent double the 3:15 monthly average watching mobile video, while accounting for 19% of its audience. Those aged 25 to 34 made up the single biggest slice of mobile video watchers at 32% but averaged only 2:10 per month. The coveted 18 to 24 demographic made up 12% of the audience and hit the 3:15 viewing average on the nose.

Forrester Research Wednesday released separate data on consumer technology use showing that 8% of U.S. consumers own a smartphone. As smartphones account for a disproportionate amount of mobile data use, the mobile video audience should rise along with the spread of higher-end devices. Gartner forecasts smartphones to grow to 45.5% of all mobile phone sales worldwide by 2013.