From 1997 to 2003, there was a decline of 50 percent in the proportion of children nine to twelve who spent time in such outside activities as hiking, walking, fishing, beach play, and gardening, according to a study by Sandra Hofferth at the University of Maryland.
Last Child in the Woods: Saving our Children from Nature-Deficit Disorder (ed. Atlantic Books Ltd, 2013) - ISBN: 9781848877498