Women who were in their late 30s and early 40s in 1960 when the Pill came along rushed out to keep from having a third-order or higher child. The drops happened within less than five years of the Pill’s appearance and were especially sharp for the women avoiding a 6th, 7th and 8th+ (all births after 8th are in one category of 8 or more) birth. The births of third and fourth children recovered a little and flattened out briefly as younger cohorts of women aged into that 35-44 age range, but then continued the drop even more steeply. The CDC graphed the declines in page 5 of their 1975 National Vital Statistics Report.
The early 1960s were pre-internet, household goods productions still sometimes was competitive with store-made goods, and food was still pretty expensive. But once women born in the wake of World War I had the chance to not keep having babies up until menopause, they jumped on it, despite living in what was in many ways still a more “authentic” lifestyle by the standards of many modern conservatives with rose colored memories or film-only knowledge of the era. There was a lot of stuff going on in the 1960s and 1970s politically and socially, but average people weren’t political then, just as they are not now. And if so many women who already had large families were jumping on the chance to not have yet another baby, it’s important to understand why and that the why was probably not for politicized reasons.