The research firm Gartner said worldwide sales of smartphones in the second quarter grew at the slowest pace since 2013 as sales in China declined for the first time. Sales grew 13.5 percent to 330 million units in the second quarter compared with a year earlier. While demand continues to increase in emerging markets, Gartner says overall smartphone sales were mixed. Smartphone sales in China fell 4 percent year-over-year. China accounted for 30 percent of total smartphone sales in the second quarter, but Gartner says its phone market has reached saturation.