Sorry, but I can't cite a reference. That statistic was quoted on TV by former Baltimore (now Indianapolis) Colts quarterback Dr. Gary Quazzo(sp?) whose son was found murdered in a FL canal several years ago. I believe Dr. Quazzo is involved in a church ministry that works with runaway teens, but I don't know anything else about him or where he got his information.
I know the number seems incredibly high, but the Dr. seemed to know what he was talking about.