The "Small" Models

J.F. Francois, Tinbergen Institute and CEPR
email: Francois@few.eur.nl internet: http://www.Dismal-Science.com/francois


Introduction
The models & how to run them
System requirements
Viewing results
Technical notes and documentation
Files in the Small directory

© J.F. Francois, 1998-2002
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Introduction
:

These examples involve a GAMS/MPSGE multi-region general equilibrium model. The set of files (found in the subdirectory "small" on the CD-ROM in the "course" directory, and installed under the "course" directory on the C: drive if the course material has been installed from the CD-ROM) provides a GAMS-based version of two standard styles of multiregion CGE models:

(1)The GTAP model

(2) Robinson-deMelo syle models.

Both models are distributed with the same region and sector structure as in the GEMPACK-based SIMPLE model. The dataset is based on the GTAP dataset version 3, aggregated as follows:

Model Regions and Sectors

regions

sectors

Japan

Rest of World

primary production

manufactures

services

Viewing social accounting data: Note that the model data (including a file in SAM format) can be viewed in the SIMPLE directory with the utility "Viewhar", reachable from the WinGEM menu under HA Files. (See the notes on the SIMPLE model.) Alternatively, you can look at the social accounting data in the GAMS data input files (see below), which are simple text files.

The basic social accounting data for Japan are summarized in the following table:

 



The Models

(1) mtrmge.gms: This model is essentially identical to the GTAP model, with the exception of consumer preferences, which are Cobb-Douglas over consumer goods in this example (instead of CDE as in the GTAP model).

Trade is Armington based, and involves transport services. Consumption, Investment, and Government take fixed shares of income.

This is an MPSGE model, based primarily on Tom Rutherford's GTAP data-based CGE model and the WTO's MPSGE-based model (written by Francois, McDonald, and Nordstrom.)

The experiments can be executed from batch files from within the Windows Explorer menu (or alternatively from within a DOS box). There are three experiment files for this model:

EXP1.BAT

a move to global free trade

EXP2.BAT

a change in domestic output taxes

EXP3.BAT

a change in consumption taxes

(2) mrtmge1.gms: This is a deMelo-Robinson style CGE model. There is a CET transform technology between exports and domestic goods. Also, government and investment demand are fixed.

The experiment here involves:

EXP4.BAT

a move to global free trade

 

(3) running the models: You can either run the models from the DOS prompt: typing (for experiment 1)

GAMS EXP1

or you can also execute the models from the Windows Explorer menu. Note: The most recent version of GAMS comes with a graphical interface: GAMSIDE. However, this is not available for student applications. The initial experiment batch file initiates a sequence of file calls, as detailed in the figure below.

 

 

System Requirements

The models require GAMS, with an installed MCP solver (MILES or PATH). A student/demonstration version is distributed on the course CD. This is sufficient to run the models. However, larger models will require a full GAMS license. The student/demonstration version is distributed with permission.

The student version of GAMS requires 19.9 Mb of free disk space. The model directory requires 85.1 Kb of free disk space. The version of GAMS distributed with the course disk is for a DOS/WIN95/WIN98/WINNT environment. (It may work with WIN2000. I just don't know.)

 


 

Viewing Results

Once you have run the model, you can view the resuls of Experiment % by using the text editor to view file EXP%TABS.TXT. Examples are presented below: Longer output files are contained in the list file EXP%.LST.

Note: The most recent version of GAMS comes with a graphical interface: GAMSIDE. However, this is not available for student applications.

 


 

Technical notes and documentation

The aggregation of this model is based on a 2 region, 3 sector version of the GTAP dataset. Much larger aggregations are possible, and many additional aggregations are available from the GTAP consortium from its web site at:

http://www.agecon.purdue.edu/gtap.

You will need to employ a version of Rutherford's GTAPinGAMS utilities to move the GTAP data (which are GEMPACK based) to a GAMS.

You can download GAMS code for GAMS/MPSGE conversions of GTAP from Rutherford's web page:
http://nash.colorado.edu/tomruth/gtapingams/html/gtapgams.html

Supporting documentation for the theory of the GTAP model is available from the following source:

[1] Hertel, T.W. and Tsigas, M. (1996) "The Structure of GTAP," in T.W. Hertel, ed., Global Trade Analysis, Cambridge University Press, Chapter 2.

Thomas Rutherford's interpretation of GTAP within GAMS/MPSGE is explained in this document:

[2] T. Rutherford (1998). "GTAPinGAMS: The Dataset and Static Model." University of Colorado, September.

More generically, modelling in GAMS/MPSGE is explained in the following:

[3] T. Rutherford (1998). "Economic Equilibirum Modelling with GAMS: An Introduction to GAMS/MCP and GAMS/MPSGE" University of Colorado, June.

Note: The models distributed here do not follow Rutheford's representation of GTAP. Rutherford employs a hybrid model, with deMelo-Robinson type macroeconomic closure rules and CET transfromations betwee exports and domestic goods. The models distributed in this package distinguish between a more or less classic GTAP approach, and that of deMelo and Robinson.

 


 

The Small directory contents

  SMALL DIRECTORY FILES

EXP#.gms

the experiment # itself

gams2tbl.gms

a routine to write results as tables

gams2tbr.gms

a smaller version of gams2tbr.gms (to facilitate running within the student license.)

gtap4001.set

set mapping information

mrtdata.gms

gamscode to process the model data

mrtmge.gms

a version of the GTAP model itself

mrtmge1.gms

a deMelo-Robinson-style model

small.gms

the model data

small.map

set definition file

small.par

paramater file

small.set

dataset definition file

readme.txt

a text-based file with instructions for working in a DOS environment

NOTE: Output files will have *.lst names. There will also be summary table files with *.txt extensions. You may want to focus on the *.txt files when comparing results.