The US banknote, the most ubiquitous currency in the world used in everything from drug deals to legally accepted tender in multiple countries, falls short of the rupee when it comes to circulation numbers. RBI deputy governor Shirish Chandra Murmu said there are three times as many rupee banknotes in circulation as US dollar bills and nearly six times as many as euro notes. While the number of notes is determined by multiple factors, including GDP growth, inflation and Interest rates, the RBI is trying to contain the cost of currency by extending the life of banknotes using polymer.