It is important to stress that the indicators shown in the database are estimates. Official gross statistics on international trade produced by national statistics institutions result in inconsistent figures for total global exports and total global imports – inconsistencies which are magnified when bilateral partner country positions are considered. The global input-output tables from which trade in value-added indicators are derived, necessarily eliminate these inconsistencies such as those that reflect different national treatments of re-exports and transit trade (as through hubs such as the Netherlands and Hong Kong, China) to achieve a coherent picture of global trade. For the countries for which data is presented, total exports and imports are consistent with official national accounts estimates. But bilateral trade positions presented in the database (based on gross flows) and those published by national statistics institutions may differ. Work is ongoing within the international statistics community to achieve coherence in international trade flows, particularly in the area of trade in services, where significant differences exist when comparing national statistics. In addition, it is useful to put the two key underlying assumptions used to derive indicators into a broader content: