CoPS/IMPACT Computing Document Number C12-01

Title: Adding Accounting-Related Behaviour to a Model Implemented Using GEMPACK

Authors: W.J. Harrison and K.R. Pearson


Many modellers need to add new behaviour to an existing model which is implemented using GEMPACK. In many such cases, the new behaviour is intimately connected with the accounting relations in the model. An example is the task of adding new taxes to a model. The aim of this paper is to give some guidance to modellers faced with such model extensions.

Most models implemented in GEMPACK are written down as systems of linearised equations. Others are written as systems of mixed levels/linearised equations or of just levels equations. Adding accounting-related behaviour to linearised TABLO Input files is probably less straight forward than adding it to mixed or completely levels files.

Irrespective of the style of the equations in the original TABLO Input file, the first task is to write down the levels equations describing the new behaviour.

New data may be required, and care must also be taken with this. In particular, the new data must be set up so that the new levels equations of the model are satisfied in the pre-simulation data base (as well as the equations of the existing model).

In the paper a relatively simple example of accounting-related behaviour is considered, namely adding a form of consumption tax to the Stylized Johansen model. The paper describes how this behaviour can be added to the standard linearised TABLO Input file SJLN.TAB for Stylized Johansen. In particular the paper shows how the new behaviour can be added as linearised equations or as levels equations.

JEL classification: C68, C88

Computing Document Number C12-01 can be downloaded in PDF format. To print this you will need the Adobe Acrobat Reader.

You can also download the example files (save as SJHT-EX.ZIP) referred to in this paper.

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