Exchange rates represent the nominal value of a national currency expressed in terms of the value of another currency. The nominal value of a national currency in a specific month or year is defined as Local Currency Units (LCU). Standard Local Currency Units (SLC) are the values of an old national currency expressed in terms of the most recent national currency against the US dollar. Annual exchange rates data are expressed as SLC and LCU against the US dollar. Monthly exchange rates data are expressed as LCU against the US dollar.