The US video game industry may be experiencing a cooling console market – monthly in-store sales of video games touched their lowest point since 2006 this past July – but gaming popularity among kids ages two to 17 is still growing at a rapid pace, according to recent findings from market researcher The NPD Group.

According to Kids and Gaming 2011, 91% of kids (approximately 64 million) ages two to 17 are gaming in the US, an increase of 9 points when compared to 2009. While the percentage of kids gaming has grown significantly across all age groups, the fastest growth has been among preschoolers, with an increase of 17 points in gaming incidence when compared to 2009. The other segments driving this growth are females and teens ages 15 to 17.

The study also found that since 2009, the population growth of kids ages two to 17 increased 1.54%  in the US, while the gaming population of that age group has grown 12.68%. Clearly, this growth in kids’ gaming population is far outpacing the growth experienced by this demo in the country.

Year-to-date through August 2011, kids comprised 44% of new physical software dollar sales, signifying an important consumer segment for the industry.  And in the past three months, kids and their parents spent more than five times as much on physical games (across devices) as they did on mobile gaming apps for smartphones and other app-capable devices.

Still, and not surprisingly, platforms such as mobile devices and computers have experienced the most significant increases in gaming activity. For example, since 2009, gaming on mobile devices is up from 8% to 38%. This growth has been mainly driven by the availability of new devices on the market such as tablets, iOS and Android-based smartphones, as well as the growing amount of content for these devices in the form of free and paid apps.