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GTAP Resources: Frequently Asked Question Details

Subject: Difference with GDP numbers in GTAP

Question: Why are the GDP (or other macro data) numbers in GTAP so much different from my country’s official statistic?

Answer: There are several reasons why this can happen. For example, our source for GDP data, the World Bank dataset, may have different definitions of a reference year for different countries. These could vary quite a bit across countries and obtaining harmonized information for all countries for 12 months in a year would be daunting task, requiring expertise from different countries as well as harmonization efforts. Therefore, we accept the World Bank numbers as harmonized enough. What is more important from GTAP’s point of view, for CGE modeling are the cost and sales shares, which are relatively more stable. What we strive to provide here is a global database, which has IO tables of different countries, linked with trade, tariff and other policy data, in a consistent and balanced manner. In that process, we may not have reached complete consistency or harmonization in one or more components of our data, to the extent that our sources have not ensured the same. It is for this reason that we request our users to be careful and exercise judgment while using the data for specific purposes.

You can match the exact GDP you want it to have via Altertax simulations. So, we urge our users to put in a bit more effort into improving the representation of the sectors and countries important for them, using Altertax, given that they have access and more knowledge of their economies. See for example, the following study, wherein the authors had done the same for a study on Egypt:
https://www.gtap.agecon.purdue.edu/resources/res_display.asp?RecordID=2466

You can learn more about Altertax at:
https://www.gtap.agecon.purdue.edu/resources/res_display.asp?RecordID=315


Source: Other

Date Added: 5/9/2013