For the beleaguered music industry, any positive news about sales is cause for celebration. And in 2011, the numbers were slightly up.

Sales of complete albums, the industry’s most profitable product, reached 330.6 million in the United States last year, a 1.3 percent increase from 2010, according to Nielsen SoundScan, which collects sales data from retailers. Some businesses might call that level of growth flat, but since album sales had fallen every year since 2004, it was a notable improvement.

Some of that marginal growth came from one album, Adele’s “21” (XL/Columbia) which sold 5.82 million copies, the best one-year sales count for any album since Usher’s “Confessions” sold 7.98 million copies in 2004.

The increases were largely driven by consumption of digital music, whose growth quickened last year after a slow 2010. Last year 1.27 billion individual tracks were downloaded in the United States, up 8.5 percent from the year before, and sales of complete digital albums reached 103.1 million, a 19.5 percent gain from 2010.