Katy's US album sales are half of Rihanna's with only two albums verses her six and TD will outsell every solo Rihanna album in the US, Australia, Brazil, New Zealand, Canada, and possibly Japan.
and you're still not getting the point that this thread is about pop records, not Hot 100 records. but to each his own. there's no need to bring up Hot 100 achievements when that's not the discussion topic