Unit-values are defined by: trade value / quantity. These unit-values are divided by the average unit-value of the previous year to obtain elementary unit-value indices, from which outliers are detected and removed. Elementary unit-value indices are then aggregated over countries and commodities, by using formulae. Finally, the unit-value indices are chained back to the reference year (2015 = 100) and used to approximate the import and export price movements.