How do you derive constant price series in USD?
Our constant price series in U.S. dollars preserve the growth rates in constant price series reported in local currency units (LCU). These growth rates are applied backwards and forwards from the 2015 current price value in U.S. dollars to estimate the corresponding constant price series. For the reference year 2015, therefore, the values in current and constant prices will be the same, whether expressed in $US or in local currency units.
Constant price series in U.S. dollars may not be published in the WDI if any of the needed inputs to this calculation are unavailable for a given country, or if time series breaks or other quality limitations preclude reliable estimation.