In 2016, the fertility rate in the United States was the lowest it has ever been.
There were 62 births per 1,000 women aged 15 to 44, down 1 percent from 2015. There were 3,941,109 babies born in 2016.
I'm sure the reasons for this are complicated and as with many things it is wrong to think monocausally, but I am not yet *that* old and when I graduated college (from a not particularly elite state school) it was perfectly reasonable, economically, for everyone I knew to: get married in a couple of years, buy a house, have a kid, and pay for all of these things, probably with a little help from your family, but not "buy a condo in Manhattan" help, just a little a bit around the edges. People didn't dream of or expect riches for the most part, but those things were perceived to be within reasonable reach.
Now the millennials spend all of their money on slices of vegetables on toast, so it's their own fault, really.