Teen births down 50% in the last 25 years
Childhood injury related deaths down 50% in the last 25 years
Missing children down 30% in the last 15 years
is what ten minutes of Googling tells me.

Which begs the question of trends in protectiveness, because are rates low due to alert parents or are they largely independent. It's awkward to know the balance; I'm the over-protective one and still hold my eight year old's hand most of the time in a parking lot.