Adele's 'Someone Like You' Holds No. 1 on Hot 100 for Fifth Week; Rihanna, Drake on the Rise
Adele's 'Someone Like You' Holds No. 1 on Hot 100 for Fifth Week; Rihanna, Drake on the Rise

With 3.4 million sold since its debut in February according to Nielsen SoundScan, Adele's XL/Columbia album "21" is the fastest-selling release of any year since 2005. The last set to sell at a quicker clip was 50 Cent's "The Massacre," which had sold 4.5 million through the week ending Sept. 11, 2005.

Plus, "21" is by far 2011's biggest-selling album and seems a lock to take home the honor once the year ends.

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Currently, 2011's year-to-date top five selling albums in the U.S. are "21," Lady Gaga's "Born This Way" (1.77 million), Lil Wayne's "Tha Carter IV" (1.18 million), Mumford & Sons' "Sigh No More" (1.16 million) and Jason Aldean's "My Kinda Party" (1.13 million).

Columbia expects "21" to sell a cumulative 4.5 million by Dec. 31, with its sales climbing to between 5 million and 6 million by next March. The latter figure will include the sales bump the album will likely gain from next year's Grammy Awards (Feb. 12) -- where Adele seems poised to take home at least a few trophies.

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Statistically speaking, it's almost impossible for any upcoming album release to pose a threat to "21's" likely year-end dominance.

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Since 2000, the only time a year's top seller was released in its last five months was in 2007: Josh Groban's "Noel" sold 3.7 million units in three months' time. The Christmas collection was released Oct. 1 and surpassed the "High School Musical 2" soundtrack (3 million) as 2007's top seller.

Diving deeper, it's rare for a late-in-the-year title to surpass 3 million copies. There simply isn't enough time to rack up those kinds of sales.

There have been only 11 albums since 2000 that were released after Aug. 1 that sold 3 million by year's end. And since 2005, it has happened only twice: "Noel" with its 3.7 million and Susan Boyle's "I Dreamed a Dream" with 3.1 million (2009) following its Nov. 24 street date.

However, that's not to say "21" will absolutely, positively end up as the year's biggest-selling album. There could always be a left-field hit (Boyle, anyone?) that takes everyone by surprise. Or perhaps, far worse, a tragedy that sparks a massive sales surge for a beloved act. Finally, we may see "Noel"-sized sales from Michael Buble's holiday set, "Christmas," due out Oct. 24.

Every year since "Noel," we've been looking for, well, the next "Noel." There have been Christmas contenders from Enya, Sting, Chris Botti and Boyle, but Buble certainly seems a sure bet for blockbuster sales. His last studio set, 2009's "Crazy Love," has sold 2.1 million, while his holiday EP "Let It Snow" has moved a handsome 1 million since its bow in 2003. Collectively, the pop singer's catalog of albums have shifted 12.9 million since his first release dropped in early 2003.