you could tell a tremendous amount from people just from their facebook likes. almost how they base their likes. are they neurotic. wu-tang clan fans mostly hete heterosexual men, they wanted to take those traits, match that up with voter data from voter databases and create this rich idea of who is out there, and what messages are going to best resonate with them. did it work? it is a very big question. and it is not entirely clear. >> no. that comes through in the article. the other big thing here is this is as much a cambridge analytica story as it is a facebook story, maybe more a facebook story. how much did facebook know when did they know it and what are they doing about it? >> so, facebook knew about it by december 2015. they quietly went out and tried to get everybody to delete the data. we saw the letters they sent to various people sent to cambridge