Yesterday i looked in the Highscores of cod ww2 and i saw that in the multiplayer are 9.4 million users played minimum 1 round. We know that some people only play the story or others only play the zombiemode. So we can estimate that codww2 sold 10 million copies on Xboxone reatil+ digital which means that there is a very high ratio for digital at around ( 45%)
I wrote this on the gamepage of codwwII (Xone) too.
So it would be interesting to know how much players are registered on the ps4 and the pc at the highscore lists on each platform with that we would know how big every multiplayer fanbase on every platform is and we could estimate if a game is overtracked or the ratio between retail and digital is lower.