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GTAP Data Bases: GTAP 5 Data Base Bugs and Issues

Error in Export Tax Equivalent for Some Regions
Posted on Aug 18, 2003
Incorrect rates of export tax equivalent for ATC quotas were inadvertently imposed on some regions due to an error in the trade-weighting process. The affected regions are those for which there is virtually zero bilateral on textiles and/or wearing apparel with Canada, USA, EU or EFTA member countries. The bilateral transactions include textile and wearing apparel trade of Uganda, Botswana, Malawi, Mozambique, Tanzania, Zambia, and Venezuela. This error is not reflected in the tax rates file where export taxes are calculated from the trade matrices (VXMD/VXWD) but is reflected in the MFRV header which reports the export tax/subsidy equivalent of the MFA quota premia. The difference between the value of exports at market and world prices (VXMD - VXWD) should be equal to the sum of ordinary export subsidy revenue, XTRV, and (MFRV). For the regions where there is an error in the ATC export tax equivalents MFRV > VXMD - VXWD - XTRV. The error was identified by Robert McDougall in the case of exports of wearing apparel from Uganda to the USA. This bug will be addressed in a subsequent release of the Data Base.

A different error in the ordinary export subsidy revenue (XTRV) was identified in the case of exports of water transport (wtp) from Morocco. The export tax revenue was extracted from information in the input-output table. Since the revenue data was not compatible with the trade data (VXWD < XTRV), the information was not used in the calculation of export tax rates. However, the export tax revenue data was inadvertently included in the XTRV header. This bug will be addressed in a subsequent release of the Data Base. Thanks to Yvan Decreux of CEPII for identifying this error.


Non-zero Intra-USA Trade, Tariff, and Export Subsidy Data
Posted on May 20, 2003
The USA region in the GTAP 5 Data Base is composed of four standard 'countries', namely: the USA and the U.S. territories - American Samoa, Guam and the Northern Mariana Islands. Initial processing of the bilateral trade data is done at the standard country level. Although there is no merchandise trade data within the USA region, non-zero intra-USA trade is introduced when estimates of expenditures by travelers and services trade data between the USA and its territories were included in the trade data.

Agricultural tariff data in the GTAP 5 Data Base was sourced mostly from the Agricultural Trade Policy Database. Agricultural export subsidy data was contributed to GTAP by Aziz Elbehri of ERS/USDA. Both agricultural tariff and agricultural export subsidies were obtained as average rates for a region and not as bilateral rates. In constructing the protection Data Base, the same average rates were simply assigned to all trading partners of a region using the bilateral trade data as weights. The non-zero intra-USA tariff and agricultural export subsidy rates resulted from this bilateralization procedure using the non-zero intra-USA trade data.

Thanks to Martina Brockmeier for pointing out the non-zero intra-USA tariff and export subsidy rates. This bug will be addressed in a subsequent release of the data base.


Tariff Data for SACU
Posted on May 10, 2002
The Southern Africa Customs Union (SACU), composed of South Africa, Lesotho, Swaziland, Namibia, and Botswana, is represented by two regions in the GTAP 5 Data Base -- Botswana (BWA) and Rest of SACU (XSC). The same tariff rates are reported for agricultural commodities in these two regions using data obtained from the Agricultural Trade Policy Database. For merchandise tariffs, however, since the source data set from the WITS system covers South Africa but not Botswana, the tariff rates for Botswana were inadvertently extracted from the Botswana input-output table. The tariff rates are therefore different between the two regions and this is not consistent with their being in a customs union. Thanks to Terrie Walmsley for pointing out this problem which will be addressed in a subsequent release of the data base. Interested users may use ALTERTAX to alter the Data Base to assign to BWA the same merchandise tariffs as in XSC.


Agricultural Export Taxes/Subsidies Data
Posted on Nov 28, 2001
Data on agricultural export subsidy rates was contributed to GTAP by Aziz Elbehri of ERS/USDA. As reported in his documentation, the agricultural export subsidy rates were calculated from the value of 1998 export subsidy expenditures notified to the WTO and on the 1998 FOB value of exports, from UNCTAD trade data. For countries and commodities not covered in the protection data sets, GTAP typically extracts protection information from the regional input-output tables. A bug was introduced when all zeroes, whether actual zero export subsidy rates or missing data, in Aziz Elbehri's data set were inadvertently replaced by export subsidy/tax information from the regional input-output tables. This problem mostly affects Brazil, Uruguay, Australia, Hungary and Canada, since the I-O tables of these countries report some agricultural export taxes/subsidies. Thanks are due to Troy Podbury of ABARE for alerting GTAP to the problem. This matter will be addressed in subsequent releases of the data base. In the meantime, interested users may use ALTERTAX to eliminate the erroneous agricultural export tax/subsidies prior to running their simulation.


Japanese Export Taxes
Posted on Nov 28, 2001
Erroneous export taxes are reported for Japan in the GTAP 5 Data Base. This is reflected as large positive entries in the export tax revenue (XTRV) header in the main Data Base file and as negative ad valorem export subsidy rates (RTXS) in the tax file. Thanks are due to Mantaro Matsuya of the Economic and Social Research Institute, Cabinet Office (Japan) for pointing out that the export taxes are erroneous. They were derived from the Japanese input-output table submitted to GTAP. A revised Japanese input-output table will be used in subsequent releases of the data base. In the meantime, interested users may use ALTERTAX to eliminate these Japanese export taxes prior to running their simulation.


Non-zero Intra-regional Trade of Energy Commodities
Posted on Nov 28, 2001
The GTAP 5 Data Base reports non-zero intra-regional trade in energy products (col, oil, gas, p_c, ely). This can be seen in the trade-related headers -- VIMS, VIWS, VXMD, VXWD. These trade value flows should be zero for intra-regional trade of single countries in the Data Base. The problem was introduced when the original merchandise trade data was updated with trade data for energy commodities. Thanks are due to Ken Itakura for alerting GTAP about this bug in the Data Base. The problem will be addressed in subsequent releases of the data base.


Subsidies on Imported Intermediate Inputs
Posted on Sep 4, 2001
A bug related to subsidies on imported intermediate inputs used in agriculture has been identified. It was introduced by an error in indexing of imported intermediate inputs. This is explained in more detail below.

How does this error affect the Data Base? To the extent that the share of imported intermediates is zero or very small for a particular agricultural commodity and/or for a particular country, the bug will not significantly affect your simulation results. In general, this is true for majority of the countries in the Data Base. However, the bug may seriously influence the simulation results for some regions, including Sri Lanka, Canada, Peru, Greece, and Ireland. It should be of particular concern to those who are focusing on agriculture-related simulations.

A table summarizing the average intermediate input subsidies (applying to both domestic and imported inputs) for each agricultural commodity in each country is now available. It shows the differences between the average input subsidy rates in the incorrect Data Base and in the corrected Data Base.

An updated version of the GTAPAgg Data Base file is now available. The file, GTAPAGG.DAT, is an encrypted Data Base and can be of use only to the Data Base subscribers who have the GTAPAgg 5 Data Base.

A patch package for the GTAP 5 command line aggregation package is now available. The patch consists of scale factors that should be used in conjunction with the current Data Base in order to create a corrected Data Base. The package also includes a slightly revised aggregation program to address an error in the aggregation of VTWR (margins on international trade). The patch should be used only with the command-line GTAP 5 aggregation package.

For your further information, we obtain data for intermediate input subsidies from the OECD PSE data set. Only the total subsidy payments data for each produced agricultural commodity is available. The data is not disaggregated by inputs and by input source, i.e. domestic or imported. The allocation of the total subsidy payment across different inputs and across input source is done as part of building the Data Base. The total subsidy payment for each agricultural commodity is allocated so that a common input subsidy rate applies to all non-energy inputs used in producing that commodity. Energy inputs are excluded from the calculation because we impose a separate set of taxes for energy usage.

The indexing error occurred in allocating the input subsidy payments for imported intermediate inputs. Instead of applying a common input subsidy rate to all imported inputs used in producing a given agricultural commodity, the common rate was erroneously applied to a given imported input used across all agricultural commodities. This error occurs only for imported intermediate inputs and not for domestic inputs.


Aggregation of VTWR (margins on international trade) in the command-line aggregation program
Posted on Sep 4, 2001
A bug related to the aggregation of the header VTWR has been identified. The original aggregation program erroneously allocated the international margins only to the margins commodities and not to the traded commodities. This error is true only for the command-line aggregation package. It resulted in unbalanced simulation results. Thanks are due to George Verikios of the Productivity Commission (Australia) for alerting GTAP about this problem. It has now been corrected and the corrections are incorporated in the patch package for the command-line aggregation program above.