Retail sales of diamond jewelry grew last year and in the first half of 2015 by 4 percent to 8 percent with solid performance from the U.S. Meanwhile, the Chinese market continues to slow, due to stagnant GDP growth, which caused a ripple effect across the entire value chain. In 2015, diamond producers and mid-segment companies should anticipate a 10 percent to 20 percent decrease in revenue with diamond jewelry sales to remain near flat.