Adele speaks as she holds her award for best British female solo artist during the BRIT Music Awards at the O2 Arena in London February 21, 2012. [Photo/Agencies]

British singer Adele's Grammy-winning "21" scored a rare feat in 2012 as it topped US album sales for a second straight year, beating out US country-pop star Taylor Swift's "Red," Nielsen Soundscan said on Thursday.

It was the first time a single album had been a top-seller for two years in a row since Nielsen began tracking album sales in 1991, the organization said.

But US album sales overall fell 4 percent in 2012 to 315.96 million albums, after 2011 saw a rare 3 percent bump in sales.

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Adele's "21" sold 4.41 million units in the United States in 2012 to top Swift's "Red," which sold 3.11 million copies. In 2011, "21" sold 5.82 million units.

"It's a sort of a once-in-a-lifetime album," Keith Caulfield, associate director of charts at Billboard, told Reuters of "21". "Only a few of these albums come along in history."

The heartbreak record, with hits like "Rolling in the Deep" and "Someone Like You," earned Adele six Grammy Awards in early 2012, boosting the profile of the 24-year-old singer and songwriter, who records on indie label XL Recordings.

The album sold at a furious pace, reaching the 10 million albums-sold plateau in the span of two years, Caulfield noted. The last album to achieve that feat was boy band 'N Sync's "No Strings Attached," which was released in 2000.

"It's really the right combination of artistry and hit singles," Caulfield said of "21's" success.