Lewin thought that this idea of friends as fast fashion—easily acquired, 
    emotionlessly discarded when worn out—might be spurred by the United 
    States’s high level of residential mobility. American society was mobile in 
    his day and has only gotten more mobile since.

How does the author square this with all of the recent studies that show that American residential mobility is at an all-time low? [1] And yet it doesn't seem that the average American is making more deep friendships, even though he or she is staying for longer in a single metropolitan area.

[1]: https://www.washingtonpost.com/news/wonk/wp/2013/05/11/why-a...