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GTAP Data Bases: About Re-Exports

Re-exports are not permitted in the GTAP Data Base. If you suspect your data includes re-exports or the value of exports exceeds production (and/or imports exceed total domestic demand for a commodity), indicating re-exports, then these re-exports need to be removed from imports and exports.

For each commodity with re-exports an estimate of the proportion of exports which are re-exports must be determined. Using this proportion the value of re-exports can be obtained.

RX(i) = PROP(i) x X(i)
RX(i) is the value of re-exports of commodity i
X(i) is the total value of exports of commodity i
PROP(i) is the estimated proportion of total exports of commodity i which are believed to be re-exports

These re-exports are then subtracted from total exports of that commodity and from total imports of that commodity, to ensure that the SAM balances. If the demand for domestic and imported commodities is known then re-exports will have to be taken out of imports by use. If information is available on the sector/s re-exporting this commodity, then the re-exports can be taken directly out of the imports of commodity i by this sector/s; otherwise a pro-rata system can be used to reduce imports across all uses/sectors by the same proportion.

If the data does not distinguish between the use of imports and domestic commodities, then re-exports should be removed prior to splitting imports and domestic commodities. (see Domestic vs. Imported Goods).

Note: if PROP(i) is unknown and no data can be obtained the following proxy could be used.

In a SAM the following identity holds for each commodity (i): M(i) + P(i) = X(i) + A(i)
M is imports
P is production
X is exports, and
A is absorption

Then PROP could be estimated using the following formula. Note that this formula should only be used when there is NO other available information on re-exports:

PROP(i) = M(i) / [M(i) + P(i)]