Tallying sales of greatest hits albums

This question has been nagging me for awhile, but with last week’s release of a new Eagles greatest hits package I figured now was a good time to bring this up. As some of you may know, the Eagles “Greatest Hits Vol. 1” has been the biggest US catalog seller for years, with “Vol. 2” pretty high up on the list also. With this new release presumably the sales for the older volumes will probably drop precipitously (these were straight CD ports of the original albums and hence top out at about 45 minutes apiece).

So my question is one of marketing. Obviously having the biggest selling album of all time (or even one of the top 10) is a big selling point. But what happens when an upgrade of the original compilation comes out? Do they start back at square one saleswise for the new album? I would imagine this to be the case for the new Eagles hits CD, but occasionally an old greatest hits album is reissued on CD with the same artwork and general track listing, but with a few bonus songs thrown on. Are these reissues tacked on to the sales figures for the old hits release? Just curious.

Jeremy Ulrey
Austin, TX