Subtotals

See also More about the theory of subtotals and how to Specify Subtotals.

Suppose you ran a simulation where Japan removed import tariffs on 5 different commodities, resulting in a welfare gain of 1 million for the USA.

You might wonder, how much of this gain is due to the tariff reduction on good 1 and how much to the other goods 2 to 4.

You might try running a series of experiments, all starting from the original data, in which you removed one tariff at a time. Probably you would find that the changes in USA welfare due to each tariff shock did not quite add up to one million. The discrepancy arises from the non-linearity of the GTAP model.

GEMPACK offers a more sophisticated approach to this problem, which has two advantages:

•the changes attributed to each shock exactly add up to the effect of the whole package.

•it is rather quick and easy to do.

In GEMPACK jargon, subtotals refers to the contribution made by one shock or group of shocks to the total changes caused by all the shocks. Suppose your complete shock package was specified by

Shock tms(TRAD_COMM,REG,JPN) = select from file tms.shk;

Then, if you added the following lines to the memo on the shocks page:

Subtotal tms(EXTRACT,REG,JPN) =Extract Effect;

Subtotal tms(FOOD,REG,JPN) =Food Effect;

Subtotal tms(AGRIC,REG,JPN) =Agric Effect;

Subtotal tms(LITMNFC,REG,JPN) =Litmnfc Effect;

Subtotal tms(HVYMNFC,REG,JPN) =Hvymnfc Effect;

RunGTAP would calculate the contributions of these individual tariff cuts to the total simulation results.

The Define Subtotals button on the Shocks page help you compose these statements.

After you specify shocks, you can ask for various subtotals to be calculated by clicking on the Define Subtotal button. You specify the shocks relevant to each subtotal via the Specify Subtotals form.

The subtotals results are shown in separate columns in the results pages. The subtotals results come after the simulation result and any levels results.

Note that subtotals results can only be calculated by programs from Release 7.0 (or later) of GEMPACK.

URL of this topic: www.copsmodels.com/webhelp/rungtap/hc_subtotals.htm

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