An interesting but secondary point. Social Media is, for all intents and purposes 18 years old. The drop in fertility predates it by 40 years. Births started to drop in the 1960's because the society was coming off the post-war baby boom. In 1969 and 1970, it began to tick up, i.e. the early baby boom children were starting to have children. And then it fell off the charts.
Choices are always based on expectation. What was the change in expectations around 1970? The chart below is the percent of women between 25 to 54, i.e. after college and before the biological clock runs out, in the workforce.
If one corrects for this social change, one finds that births related to those not in the workforce have been holding up.
Needless to say, women are not having 5+ children on average. This is a rough adjustment. The important takeaway is that the biggest part of the drop is from women being convinced that working for money instead of love had the biggest effect.

Everything is a panopticon now.

Well he could tidy himself up.