So I was bored and decided to predict Britney's 9th album sales.
Since Britney's album sales are falling, I based my calculation on that.
So Circus opened with 505k and FF did 276k, that's a %-45.3 change.
FF did 276k and BJ did %-61.2

The average between 45.3 and 61.2 is 53.2, so Britney's 9th album will open with 56.9k

I did the same percentage change thing with the album total sales, and Britney's 9th LP's tally will be 152.2k
IDK, I'm bored.