Is your 9-year-old mature enough to play in a park unsupervised?

Last month South Carolina mother Debra Harrell was arrested for letting her 9-year-old daughter play in a park unsupervised while she was at work. Since then numerous other parents have also been arrested for allowing their children to play in public places, both indoors and outside, unsupervised.
As the nation debates whether such parenting choices are acceptable or neglectful, the latest Reason-Rupe national telephone poll finds 82 percent of Americans believe the law should require children 9-years-old and younger to be supervised while playing in public parks. Just 17 percent of Americans think 9-year-olds should be able to play unsupervised at the park. I'm not sure a 15 year old in today's society should.
Interested in the rest of the findings? Click here: http://reason.com/poll/2014/08/18/reason-rupe-poll-august-poll-html#parenting