We've heard a lot in recent weeks about the records being tied, set, and/or broken by Katy Perry and Rihanna -- which has made it easy to forget that Adele's '21' is still the top-selling album of 2011. Well, here's an even more impressive reminder of the 'Rolling in the Deep' singer's success: '21' not only outpaced sales of all other releases this year, it posted the biggest one-year sales total since 2004.

At 5.28 million units sold and counting, '21' has had a better year than any album since Usher's 'Confessions' moved 8 million copies in '04. Lady Gaga's 'Born This Way' was the only 2011 release that came close, selling just over two million copies during its seven months on the charts.

Adele's success notwithstanding, 2011 was another soft year for the music industry. According to Billboard's year-end report, overall sales are up one percent on the year, although sales this week are down 10 percent against the comparable sales week from last year.

Considering that the fourth quarter has delivered holiday releases from Michael Buble and Justin Bieber, those numbers have to be disappointing, although high single-digit gains in digital sales are a somewhat encouraging sign for continued growth in 2012.

Unfortunately, the music biz won't have Adele's help in 2013: she's recently gone on record as stating that her next album is two or three years away.