Concentration and risks	12 Months Ended
Concentration and risks	Dec. 31, 2015
Concentration and risks
Concentration and risks	3. Concentration and risks Concentration of customers and suppliers There are no customers or suppliers from whom revenues or purchases individually represent greater than 10% of the total revenues or the total purchases of the Group for the years ended December 31, 2013, 2014 and 2015. Concentration of credit risk Assets that potentially subject the Group to significant concentrations of credit risk primarily consist of cash and cash equivalents, restricted cash, accounts receivable and short-term investments. The maximum exposure of such assets to credit risk is their carrying amounts as of the balance sheet dates. As of December 31, 2014 and 2015, all of the Group’s cash and cash equivalents, restricted cash and short-term investments were held by major financial institutions located in the PRC and Hong Kong which management believes are of high credit quality. On May 1, 2015, China’s new Deposit Insurance Regulation came into effect, pursuant to which banking financial institutions, such as commercial banks, established in China are required to purchase deposit insurance for deposits in RMB and in foreign currency placed with them. Such Deposit Insurance Regulation would not be effective in providing complete protection for the Group’s accounts, as its aggregate deposits is much higher than the compensation limit. However, the Group believes that the risk of failure of any of these PRC banks is remote. Bank failure is uncommon in China and the Group believes that those Chinese banks that hold the Group’s cash and cash equivalents, restricted cash and short-term investments are financially sound based on public available information. Accounts receivable are typically unsecured and are derived from revenues earned from customers in the PRC. The risk with respect to accounts receivable is mitigated by credit evaluations the Group performs on its customers and its ongoing monitoring process of outstanding balances. Currency convertibility risk The PRC government imposes controls on the convertibility of RMB into foreign currencies. The Group’s cash and cash equivalents, restricted cash and short-term investments denominated in RMB that are subject to such government controls amounted to RMB9,054,762 and RMB12,630,577 as of December 31, 2014 and 2015, respectively. The value of RMB is subject to changes in the central government policies and to international economic and political developments affecting supply and demand in the PRC foreign exchange trading system market. In the PRC, certain foreign exchange transactions are required by law to be transacted only by authorized financial institutions at exchange rates set by the People’s Bank of China (the “PBOC”). Remittances in currencies other than RMB by the Group in the PRC must be processed through PBOC or other Chinese foreign exchange regulatory bodies which require certain supporting documentation in order to process the remittance. Foreign currency exchange rate risk In July 2005, the PRC government changed its decades-old policy of pegging the value of the RMB to the U.S. dollar, and the RMB appreciated more than 20% against the U.S. dollar over the following three years. Between July 2008 and June 2010, this appreciation halted and the exchange rate between the RMB and the U.S. dollar remained within a narrow band. Since June 2010, the RMB has fluctuated against the U.S. dollar, at times significantly and unpredictably. It is difficult to predict how market forces or PRC or U.S. government policy may impact the exchange rate between the RMB and the U.S. dollar in the future.