My guess is that it's based on standard How To Lie With Statistics tricks (e.g. a bookstore that carries Playboy counts as an "adult bookstore"). It's the same fast shuffle used by gun grabbers in generating statistics for "children killed by guns" -- they count 24-year-old gang-bangers and then use a label that evokes an image of thousands of toddlers stumbling upon Daddy's pistol.
that goes right along with the "but rapes are down" statistic....
like really, the world is such a great and peaceful place now...
we have no rape, we have no molestation...we have no murder ...we have no assault...
we have great families with no divorce...
we don't have people killing their spouse and kidnapping the children....
we don's have kids killing their parents and their parents killing them...
our kids our happy and well-behaved and all of them are doing so well in school, anyday now, they might get up to Japan's standards...
yep, let's just keep doing what we've been doing....(NOT!).