Two different studies on this page - with very similar information
Teenage media habits survey July 2010
http://www.businessinsider.com/the-shocking-media-habits-of-8-18-year-olds-2010-7
2000 families
Basically, if kids are awake, they're consuming media.
Following are some of the results
See Vitamin D Life
- Every hour of TV watched reduces your lifespan by 22 minutes – Aug 2011
- Many reasons why vitamin D deficiency has become epidemic
- Dark skinned teens use media much more - June 2011
That web page has the following graphic