Special drawing rights (ISO 4217 currency code XDR, also abbreviated SDR) are supplementary foreign exchange reserve assets defined and maintained by the International Monetary Fund (IMF). The XDR is the unit of account for the IMF, and is not a currency per se. XDRs instead represent a claim to currency held by IMF member countries for which they may be exchanged. The XDR was created in 1969 to supplement a shortfall of preferred foreign exchange reserve assets, namely gold and the U.S. dollar.