TiVo editors use a 1 to 5 star system. It is important to note that albums are rated only within the scope of an artist's own work; we won't compare a Miles Davis album to the latest album by Britney Spears.
Editors may choose to revisit an artist's discography, especially if an artist releases a great new album, to re-factor the earlier releases to better fit within the band's history. For example: in 1993 an editor may have given Radiohead's Pablo Honey four-and-a-half stars when it came out, being one of the best Britpop albums to date. As time goes on and Radiohead releases The Bends, OK Computer, Kid A, etc, Pablo Honey may not warrant being their highest-rated album. The text of the review is still valid, but the older rating gets adjusted.