Editor's note: Amy Gahran writes about mobile tech for CNN.com. She is a San Francisco Bay Area writer and media consultant whose blog, contentious.com, explores how people communicate in the online age.
(CNN) -- When smartphones first came out, many people wondered whether a TV-addicted culture would care to watch video on such a small screen.
New data from the Nielsen Company indicate that watching mobile video is indeed getting more popular, but it's far from a threat to the TV business.
In the second quarter of 2010, 22 million Americans watched video on a mobile device -- just under 10% of U.S. mobile phone users. Meanwhile, according to Nielsen's November State of the Media report, during this same period, 286,648 million Americans watched TV at home.
So to put this in perspective: The U.S. mobile video audience is about 0.07% the size of the U.S. TV audience.
Still, a mobile video audience of 22 million people is nothing to sneeze at. And that group is growing.
According to Nielsen, "In the second quarter of 2010, more Americans watched video on their mobile devices than ever before. On a year-to-year basis, the number of people watching mobile video increased more than 43%, while the amount of time spent doing so was up almost 7%."
Nielsen reported that Americans who watch video on mobile devices do so for an average of 3½ hours per month, but that varies greatly by ages. Americans age 17 and under who watch mobile video do so for more than seven hours per month; for those age 50 and over, it's just more than two hours per month.
Nielsen didn't say which kinds of videos people are watching on mobile devices, but I suspect it probably comprises mostly YouTube videos and news, music or sports footage, rather than full-length movies and TV shows.
Nielsen's numbers include video viewed through smartphone and tablet apps. But they do not include mobile games, which are a hugely popular and often video-rich mobile activity.