Customers shop at a duty-free mall in Sanya, South China's Hainan Province. Officials from Hainan said on Monday that sales of duty-free goods amounted to nearly 100 billion yuan ($15 billion) in the past 10 years, and the number of shoppers exceeded 25 million. Duty-free sales account for about 40 percent of Hainan's domestic tourism revenue. Photo: cnsphoto