Does "being affected" mean reduced? Because they're not losing out on ad revenue they would otherwise gain. That's the piracy argument with ads: if only everyone who used our product would pay us what we want, we wouldn't be losing so much money. You can't count browsers with ad-blockers as lost revenue. (You also can't count search engines, REST and curl, etc... as lost revenue.)
> then how can they decide if a change in revenue source is necessary?
Shouldn't a change in revenue model be driven by the opportunities of a subscription (or other) model, not by issues with advertising?
It seems like you're selling a service that will make your customers unhappy about reduced revenue, which they can't do anything about. What can a customer do differently if they find 16% using ad blockers, or 34% using ad blockers? Their ad revenue is the same regardless of the percentage. Their other revenue models haven't changed. All that's changed is that now they're mad about users with ad blockers. At best, if the percentage is going to drive a decision about changing revenue models, all they really need is a single data point, not a monthly service.
> why are you opposed to websites knowing how many of their visitors are blocking ads?
Because people aren't rational. They'll get angry about a transaction cost of the advertising model, and do all the same stupid things we saw 2 or 3 years ago: rants of moral indignation, poorly implemented content blocking, big obnoxious pleas, etc...