I was somewhat involved in (relatively early days of) real time bidding and targeted advertising, circa 2010 or so. My data at the time led me to believe that

I was somewhat involved in (relatively early days of) real time bidding and targeted advertising, circa 2010 or so. My data at the time led me to believe that there is a small-ish part of the population on which targeted advertising is effective, and all the effort (information-theoretic wise) is locating this group, when your only tool (in real time bidding, anyway) is bidding on random ad impressions. I’m sure the world is different now, and this inight might not be relevant to today’s world. But it does explain why re-targeting is way more effective than most people assume.