Boom of interactions on mobile devices for US children.
It is the result of a survey by Common Sense Media, which interviewed a sample of 1500 families with children in that age range. That's currently a third of the number of children reading books every day. It is an important transition phase, not necessarily negative: just consider the data of children under 8 years old engaged in an activity that is often much less interactive: that of watching TV. 58% of kids do it every day, passively. Are we sure it's not a (mild) improvement? Of course it would be better if outdoor activities increased (but yes, I rediscover myself as 'old fashioned') but if they really have to deal with an electronic device, even better internet than TV. 
