Mary Pipher and Sara Pipher Gilliam

Many girls report that their mothers are their best friends. The close-knit family unit has, for the most part, rebounded as divorce rates have dropped to a 40-year low.

But girls today aren’t as self-sufficient as their counterparts in earlier decades: They are less likely to possess driver’s licenses, work outside the home or date.

They are also more solitary. Research from the University of Michigan’s Monitoring the Future project shows that, since 2007—the dawn of the smartphone era—girls have dramatically decreased the amount of time they spend shopping, seeing friends or going to movies. We found that many girls spend their Saturday nights home alone, watching Netflix and surfing social media.