The format may end with a whimper, but some albums are going out with a bang. Despite declining album sales over the past decade, a few releases with broad appeal still manage to reach the marathon milestone of 10 million copies sold.

Usher was just ushered into that elite circle, and Adele is poised to be next.

Usher's Confessions crossed the threshold in the week ending July 1, eight years after its release, becoming only the 19th album to do so since Nielsen SoundScan began tracking data in 1991. It sold 1.1 million copies when it bowed at No. 1 in Billboard in 2004 and 2,000 copies the week it inched past sales of 10 million.

Adele's 21, already a catalog of sales records, has sold 9.57 million copies since its U.S. release in February 2011, according to Nielsen SoundScan. It still sells as many as 50,000 a week and "is most likely to join the 10 million club next, probably before the end of the year," says Keith Caulfield, Billboard associate director of charts.

Reaching that benchmark is a tough haul, especially in the digital era.

"The bulk of the 10-million sellers came in the late 1990s and early 2000s during that golden era of record sales," Caulfield says. "It's rare for any album to sell that many copies, period. But with album sales the way they are now, it's increasingly rare. People cherry-pick the tracks they like. They may be streaming songs on YouTube or Spotify. And certainly piracy has factored into it.

"It speaks to the popularity of those albums that reach that plateau," he says. "Adele has been able to defy all those obstacles. To sell 10 million copies of one album in one country in less than two years is monumental."

Caulfield likens 21's reach to Santana's 1999 Supernatural, the Grammy magnet that sold 11.73 million copies, ranking seventh on SoundScan's list of best sellers. Adele crafted "the kind of album that keeps finding new fans every week. People who are not huge music fans may have 20 or 30 albums, and now Adele is on their shelf next to Thriller and Elvis Presley and The Beatles."

Even closer to scaling the peak are Linkin Park's 2000 debut Hybrid Theory with 9.98 million and Pearl Jam's 1991 debut Ten with 9.96 million, but neither has the sales momentum to stave off Adele's juggernaut. Before Usher, the last album to sell 10 million was Eminem's The Eminem Show, which hit the mark in 2011, nine years after its release. SoundScan's biggest seller is Metallica's self-titled 1991 "Black Album," with 15.79 million.

USA Today