20 million long ago

[Villavic]

I agree about the world wide number. I read in Mick's book or other source, long ago (1992?) that Rumours had reached 20 million copies (Thriller was 40 million).

And Thriller was followed but Saturday Night Feve and/or Grease.
Then Rumours.

But then I have heard about Madonna's albums, Eagles, the Boss, etc. I don't know about record sales in the world. Who have the most exact and official register? Billboard? Guinness?