New ask Hacker News story: Ask HN: Is there any proof/studies showing targeted ads improve sales?

Ask HN: Is there any proof/studies showing targeted ads improve sales?
2 by massung | 2 comments on Hacker News.
With the recent announcements of Brave buying a search engine and Google changing how some of its targeting works (not using as much personal data?), I'm curious if anyone in the know has direct knowledge of evidence whether or not targeted ads really has an impact on clicks and actual purchases or not? I had remembered reading about companies/advertisers suggesting that the extra $$ dumped into targeted ads on FB resulted in no extra revenue they could tie to that campaign. Sorry, I know that without links it's just a vague recollection that could be wrong. Obviously this question has no bearing at all on whether or not personal data collection and mining has value (it does, even if not monetarily - e.g. at the state level).