Zimbabwean dollar
After the revaluation of the Zimbabwean dollar on 1 August 2006, the đồng became the least valued currency unit for months. Around 21 March 2007, the revalued Zimbabwean dollar regained least valued currency status (in terms of black market exchange rate), and on 7 September 2007 in terms of official exchange rate. After the use of the Zimbabwean dollar ceased on 12 April 2009, the đồng was the second least valued currency unit after the Iranian rial as of 28 November 2014. Since 19 June 2014, the Vietnamese dong has been devalued a total of five times in an effort to help spur exports and to ensure the stability of the currency.