For the last year or so, the music industry has been buzzing with optimism that its fortunes have finally begun to turn around after more than a decade of digital disruption and plunging sales. Now it has proof.

On Thursday, the Recording Industry Association of America, the trade group that represents the major labels, reported that music sales in the United States generated $7.7 billion in retail revenue in 2016, up 11.4 percent from the year before. That is the industry’s highest sales figure since 2009 and its best percentage gain since 1998.

The increase is largely the result of online streaming, which is rapidly eclipsing all other forms of consumption. Streaming contributed $3.9 billion in 2016, up 69 percent from the year before, and now makes up 51 percent of the business — the first time it has had a majority of sales in the United States.

The largest and fastest-growing chunk of the streaming business is in paid subscriptions to services like Spotify and Apple Music. In the United States, services like these attracted an average of 22.6 million subscribers and generated $2.3 billion, nearly doubling their total from the year before. Spotify has said that it has 50 million global subscribers, and Apple Music has more than 20 million.