Hungary was supposed to join the eurozone in 2010, which would have resulted in the MNB losing control of monetary policy, but central bank leaders criticized this plan, saying that the fiscal austerity requirements would slow growth. In December 2011 two of the three major credit rating agencies downgraded Hungarian long term currency debt to "junk status", due in part to changes to the Constitution of Hungary, creating doubts about the independence of the central bank. On 20 May 2016, Fitch Ratings upgraded Hungary's corresponding debt status to BBB- (which is investment grade), assigning a stable outlook to the rating. The upgrade was mainly motivated by, among other factors, high current account surpluses, high European Union (EU) fund inflows, banks' external deleveraging, the central bank's self-financing programme and foreign currency mortgage conversion reducing Hungary's external debt and financial vulnerability.