iOS impressions down 30% from peak is "not a huge deal"? This is very counterintuitive to me, as iOS both holds the majority share of the US market, and 30% seems like a very high number. Can you explain?
The discrepancy is that a 75% reduction in users opting into Facebook tracking is leading to only a 30% reduction in iOS share on the highest ROI ad campaigns. 30% is big but not 75% big.
Another possible explanation is that opting out of tracking in iOS doesn't make you invisible. It just makes it hard for Facebook to correlate your off-app/non-Facebook.com web activity, but there are ways around that. So what 30% means hinges a lot on how the 1st touch -> 2nd touch leap is done, and the data for that leap doesn't always come from Facebook.