Is sexually charged material in music, magazines, tv and movies the cause of teenagers being sexually active earlier?

http://www.heraldsun.news.com.au/common/story_page/0,5478,18695106^663,00.html

on a slightly different note;

http://www.heraldsun.news.com.au/common/story_page/0,5478,18679120%5E663,00.html