> Are generations really demographic pulses as you describe?

Here[1] is the US population pyramid. You can clearly see the small increases and decreases at various ages - a demographic pulse, as you said. There is a significant decline in the echo currently at ~14 in that image. I would note that early adulthood tends to bring in more immigration (people moving for university and staying), so I wouldn't read too much into it at this point.

[1] https://en.wikipedia.org/wiki/File:USA_Population_Pyramid.sv...