Re injury, rates have gone down due to better product design and safer roads and cars, IIRC.

Re teen births, as I said, teen sexual activity is down and birth control use is up somewhat. It could be related also to parents talking to their teens about safe sex and their expectations regarding sex (proven to work!)

Re missing children--well, that's a tricky one, and possibly the real question for the free-rangers. Are there simply fewer child abductions because nobody's children go out to play alone or walk/bike alone anymore? Or is the world actually safer now for children alone?