The best way is to use your brains and knowledge!
How was this list built (the part that was opted for, not the scrapped part)? How big are these two portions? Can they be segregated? Was the opted-in portion interested in a few certain things? The scrapper part - what was the source and constraints for scrapping? And so on.
You can get meaningful results only if you do meaningful activities, which can only happen if you combine your mind (brain) with knowledge.