From my email:

Hi folks, appreciate the discussion of the piece here, as ever.

I just wanted to chime in briefly with an analogy that speaks to one of the ways I think about the causal mechanism here, and to my mind pushes back against the argument that since past declines in fertility didn’t come from smartphones etc the current decline can’t either.

• ⁠In the past, weight loss generally came from sustained dieting and exercise
•⁠  ⁠⁠Now it overwhelmingly comes from injecting GLP-1s
•⁠  ⁠⁠In the same way that GLP-1s are a technological shock that amplifies/accelerates the old mechanism (eating less), social media is a technological shock that amplifies/accelerates the old mechanism (cultural change)

To my mind one of the ways (possibly the main way) that phones and social media could be affecting fertility is by accelerating and internationalising pre-existing trends of cultural change. One example could be young women’s sense of empowerment and independence, which was on the rise in many parts of the world but has sped up over the past decade or two (I would point to my previous work on the ideological gender divide as one piece of evidence here) and has spread rapidly to regions and cultures that were surely very unlikely to reach this point without exposure to western social media.

Thoughts?

I will add one point on this debate, noting I do not think it runs counter to Burn-Murdoch.  Some commentators are insisting that what really matters is how many children survive to adulthood, not how many are born in the first place.  But both numbers matter a good deal.  Every time a woman gets pregnant she incurs significant costs, especially in older times when death in childbirth was common, or even death or health problems from a miscarriage were a much greater risk.  Furthermore, if you tried for seven kids, but only expected three or four to survive, a lot of times more than three or four survived.  So general survival of all or almost all your children had to be a palatable option, even if the expected value was lower than that.