I don’t want to be flippantly dismissive but surely there was a certain other event in 2008 that caused many families to reconsider the financial wisdom of starting a family.
Since people using other carriers also experienced 2008, it's not that.
Alternatively, maybe you are arguing that even if iPhones caused a decline in birth rate among tech hipsters, that doesn't transfer to the population at large. This is both less believable and less valuable as a criticism of the study: even if the result only holds in one demographic group it's still an interesting finding.
Sheesh, when the addictive scrolling was scrolling through your emails and BB Messenger messages...
Or maybe the type of person that buys iPhones also spends too much on other items causing them to be over leveraged when a financial crash does occur.
With that said, I can also see that infinite entertainment and infinite information makes you deprioritize having children.
But it’s far from proof, this study. It’s more like “I found some numbers that support my already existing opinion, so let’s run with that”.
Now ~20% of all pregnancies in the US are 35+.