What you're really saying is National Park crime rates are vanishingly small, calculated against recreation visits. National Park Service, 2010:

All units--281,303,769
National parks--64,623,855

Perhaps a new slogan is in order: "Your National Parks--safer than any suburb could dream of being."

And as all backpackers know, the farther away from the parking lot you get, the safer you become. First rule of lightweight backpacking: items left at home are the easiest way to lighten your pack.

Cheers,