I worked at a massive adtech company and we had our own unique ID for each "entity". All other data was gathered with cookies and some sort of compaction/merging algorithm. What would we do with the social? Run a credit report on every single one then only show ads to those people? Re run it every so often for updates?

I wasn't a developer but we already had income estimate by looking at past purchases, location, sites that the person looked at, etc. It wasn't super accurate but enough to know whether someone should see a Fendi bag