Exports and imports cover movements of goods across customs borders; generally, exports are valued f.o.b. (free on board) and imports c.i.f. (cost, insurance, and freight).
The primary source is COMTRADE, the UN trade data system, made available through the UN Statistical Office (UNSO). The data are based on countries' customs returns. The data may differ from trade data reported by other agencies because of differences in the valuation, concepts and definitions, exchange rate conversion, coverage, estimation method, vintage, etc. A major effort is currently under way to rectify these differences; this effort may eventually reduce or eliminate these differences.
Data for the most recent years for many countries, particularly developing countries, are often obtained from other sources or estimated by World Bank Staff.
Export and import price indexes for developing countries are World Bank estimates; for industrial economies, the indexes are taken from other sources such as the UN' s Monthly Bulletin of Statistics and the IFS. The price indexes may differ from those reported by other agencies because of differences in the estimation technique, base year, and/or rebasing procedure, etc.