[InSteady]

You raise an interesting point, but you also seem to be conflating two things. Having children is more expensive than ever, and purchasing power has continued to drop for decades. Not to mention the drastic increase in specific "raising a family" essentials/barriers like housing costs, medical debt, educational debt, and childcare expenses. I don't have numbers to back this up, but my intuition (based on observation and casual reading) is that more working class people who actively want to have children are not doing so because they are stretched too thin than we saw in the 1970's (when people could work part-time to pay for all 4 years of college and expect a high paying career out of their degree).

Also, a 15% drop in 50 years is nothing to scoff at. In America, we are below the replacement fertility rate of 2.1 children per woman. Currently it is at 1.7, so our population would be declining without immigration. [1] This is not a bad thing in my opinion, but it is extremely significant in terms of politics, culture, and economics. If our fertility rate continues to drop expect to start hearing about it more often and at higher volume from many different corners.

[1] https://www.cdc.gov/nchs/data/vsrr/vsrr028.pdf