The index numbers, which reflect the percentage rise or fall of unit value and volume levels were first constructed with 1970 as the base year (1970=100) and then base year 1999=100. Currently, the indices are rebased to 2005.

The external trade unit value and volume indices are key economic indicators which have a variety of applications and uses.

Approximately 1,191 export items representing about 90.6 percent of the total value exports recorded in 2005 and 1,941 import items accounting for about 87.5 percent of the total value of imports 2005 are used in the calculation of the index of imports and exports, respectively. The Indices are based on the concept of a fixed basket of commodities.