Reconciling Bilateral Trade Data for Use in GTAP

Bilateral trade flows are reported by both importers and exporters. Large discrepancies in reported import/export trade flows can be found when these two reports are compared. The GTAP Data Base requires consistency between the export flow and its corresponding import flow for all partner pairs. Therefore, bilateral trade data in its reported form cannot be directly used for GTAP. Various methods can be used to produce a consistent set of bilateral trade flows. However, achieving consistency alone does not necessarily provide credible trade flows. Matrix balancing using trade totals published by international agencies is not appropriate since these totals are not reconciled but are simply totals from country-reported flows. A method is developed with the aim of extracting the most reliable reported trade flows from reported import and export flows. Specific examples are used to illustrate how discrepancies can result from reporting errors and transport margins. Evidence is shown indicating that discrepancies often arise from erroneous reporting by one of the partners. Systematic reporting errors associated with a reporter can be measured by the share of consistent transactions with partners. The most reliable reported flows are selected based on credibility of reporters. The source of international bilateral trade for GTAP is United Nations COMTRADE database. It contains the complete set of countries in the world and the set of commodities covering total merchandise trade. Since errors in reporting are country-commodity specific, data is processed at the individual country and SITC 4-digit level before aggregating to the 30-region 31- merchandise trade commodity database in version 3 of the GTAP Data Base.