April 3, 2014 - The U.S. sales volume of carbonated soft drinks fell 3% last year, according to the annual report by Beverage Digest. This extends a trend that began a decade ago. Among the top 10 brands, Diet Coke was down 6.8% and Diet Pepsi was down 6.9%. These declines were sharper than the regular versions of Coke and Pepsi, which also declined by 0.5% and 3.6%, respectively. Diet Mountain Dew fell by 3.1%, and Coke Zero by 0.1%.