>That could still be due to technology but not social media exclusively.
the tech before social media - TV:
https://mahb.stanford.edu/blog/tv-birth-control/
"TV As Birth Control
...
The impact of the new TV programming in rural India has been profound—and very positive, say Jensen and Oster. Their interviews revealed that when the new TV services arrived, women’s autonomy increased while fertility and the acceptability of domestic violence toward women significantly decreased."
Exactly.
We've been replacing biological imparatives with strange forms of nonbiological entertainment.
And it's increased now to the point that it's in endless supply and constantly attached to us.
How can you tell that tech is the cause of people not having children, and not just what they're doing because they don't have children to fill their time?
I don't think you can point to the rise of tech as a casual just because it's popular. If people aren't having children they'll do something else instead. To say what that is you need more evidence that what people are doing.