For the second time in a row, the year in music belonged to Adele.

Her album “21” (XL/Columbia), released almost two years ago, was the top seller in 2012, as it was in 2011, marking the first time since Nielsen SoundScan began tracking music sales in 1991 that one album has reigned for two consecutive years. According to figures released last week, “21” sold 4.4 million copies in the United States last year, after selling 5.8 million in 2011. Late last year “21” crossed the 10 million mark, becoming the 21st album to do so in the SoundScan era.

The second-biggest album of 2012 was Taylor Swift’s “Red” (Big Machine), with 3.1 million sales. It is also the top album on the latest weekly Billboard album chart, compiled from sales in the week that included Christmas, selling 241,000 copies in that period.

The British boy band One Direction scored two slots in the year-end chart. “Up All Night,” released in March, reached No. 3 with 1.6 million sales; “Take Me Home,” from November, is No. 5 with 1.3 million. (Both were released by Syco/Columbia.) The fourth-biggest album of the year — and the only rock title in the Top 10 — was Mumford & Sons’ “Babel” (Glassnote), with almost 1.5 million copies sold.

The music industry had started off 2012 with a hopeful spring in its step, because it had seemingly broken a long losing streak for its most lucrative product — album sales. In 2011 — for only the second time in a decade — sales increased slightly (1.3 percent), leading some to wonder whether things were finally turning around. But in 2012, despite big numbers for a few top acts, the industry’s familiar sales pattern returned: falling album sales, with the growth in downloads not enough to offset the rapid decline of the CD.

A total of 316 million albums were sold in 2012, down 4 percent for the year. Sales of CDs were down 13.5 percent, but full album downloads gained 14 percent, to a new high of 118 million.

About 37 percent of albums are now bought digitally, while the CD continues to fade: Its sales have declined 75 percent since 2000.

One number that keeps going up, however, is song downloads, which in 2012 increased 5 percent to reach 1.3 billion. Each of the three most popular tracks last year reached the mainstream through paths that were once unorthodox but are increasingly becoming the norm.

No. 1 was “Somebody That I Used to Know” by the Belgian-Australian songwriter Gotye, which was downloaded 6.8 million times; Carly Rae Jepsen’s “Call Me Maybe” was second with 6.5 million; and Fun.’s “We Are Young” reached No. 3 with nearly 6 million. Gotye and Jepsen’s songs owed much of their success to clever videos that caught fire on social media. Fun.’s song was propelled by television, first in an episode of “Glee” and then in a commercial shown during the Super Bowl.

Another bright spot, albeit a small one, is the continuing popularity of vinyl albums, whose sales rose 18 percent to 4.6 million, the biggest that SoundScan has recorded since 1991. The top record was Jack White’s “Blunderbuss” (Third Man/Columbia), which sold 34,000 copies, bumping the Beatles’ “Abbey Road” to No. 2 after a three-year run at the top.