Those two facts can be explained, partially, as follows: People are delaying families longer now, as well as having smaller families(which maybe means you can get away with living in an apartment in a city which doesn't require cars). For example, the average age of first-time mothers went from ~21 in the 1970s, to >26 in 2014.

http://www.npr.org/sections/health-shots/2016/01/14/46281645...