ATLANTA – Americans are consuming less diet soda, speeding up a nearly 10-year slide in U.S. carbonated soft drink sales, according to new data released this week by Beverage Digest.

Ad Age reports: “Carbonated soft drink volume declined 3% in 2013, compared to a 1.2% decline in 2012 and a 1% decline in 2011, according to Beverage Digest. The category has seen declines for the last nine years, despite the industry's massive advertising and marketing outlays. Two years ago, PepsiCo committed to spend an additional $500 million to $600 million on its core brands, of which Pepsi is one. More recently, Coca-Cola committed to spending an additional $1 billion on media and brand-building efforts by 2016.”

John Sicher, editor and publisher at Beverage Digest, commented: "The industry's headwinds are not abating, and results are worsening…This puts a premium on sweetener innovation."