When Diet Coke was launched in 1982, the sugar-free alternative aimed to draw in consumers looking for a healthier drink. But diet soda is failing to revive an industry often associated with obesity and tooth decay. Since 2000, sales of soda drinks have only risen by 18 percent, and the increase is largely attributed to population growth and economic development. Strangely, U.S. diet soda sales have fallen sharply over the last five years, while sales of Coca-Cola have increased and Pepsi sales have remained stable. It seems that for consumers, sweeteners just don’t give enough of a sugar high.