LOS ANGELES – Taylor Swift’s “Red” has been an undisputed blockbuster since it was released in October. The album hasn’t left the top 10 and it has been in the No. 1 spot for much of its run. There’s only one reason why Swift’s “Red” isn’t the biggest pop album of 2012: It had to contend with the biggest pop album of 2011.

Adele’s “21,” released in the U.S. in February 2011 by XL/ Columbia, is the top-selling album of the year for the second year running. Adele’s Grammy-winning set sold 4.41 million copies in 2012, according to Nielsen SoundScan stats released by industry trade Billboard. The album in 2011 sold 5.82 million copies, giving it a to-date number well over 10 million.

Yet the good news for Adele isn’t shared by the industry as a whole. Perhaps reflective of a year in which no artist matched Adele’s runaway success, album sales for 2012 were down about 4 percent compared with those of 2011. CD sales took a large dip, down 13 percent, as the digital sector once again offered signs of growth.