One of the benefits of this multiple award process [a Platinum album is also a Gold album and so forth] is that it allows us to look at a question that commentors raised in the last post: do older albums simply have more time to become a hit, something that would bias this kind of analysis against newer albums? The answer appears to be no. If you go through the database you'll see that albums that achieved Platinum or Multi-Platinum designation almost all did so within a year of going Gold. So most of the sales do seem to be in the first year or two after release.
(In other words, the fact that there have been fewer bestsellers in the past couple of years doesn't seem to be because they haven't had time to "peak" yet.