Plenary Session IX: Running MAMS in GAMS

1
Plenary Session IX Running MAMS in GAMS

• Martín Cicowiez
• CEDLAS-UNLP
• Presentation for Second Training Workshop of the
• Project Assessing Development Strategies to
  Achieve the MDGs in Asia, Manila, March 24-27,
  2009

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Steps in Simulation Analysis

• Run base (business-as-usual) scenario
• GDP growth calibrated to trend from last 5-15
  years
• balanced and sustainable evolution of
• macro aggregates (private and government
  consumption and investment, exports, and imports)
• taxation
• debt stocks (domestic and foreign)
• Run alternative (counter-factual) scenarios for
  example
• change one or more parameters (policy tools or
  parameters beyond government control, ex, aid,
  world prices, productivity)
• fix an indicator that represents a policy target
  (ex, a health MDG) flex a policy tool (ex,
  government health services)
• Analyze and validate
• explain results for individual scenarios and
  across scenarios
• if needed, adjust data, model, or simulation
  design

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MAMS in GAMS/Excel

• Model code and database are separated
• model code is a generic set of files in GAMS
• database (including simulation definitions)
  stored in application-specific Excel files
• anything that is not specific to a database
  should appear in the model code
• if you want to correct an error, you only need to
  do it once

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General Structure

• The model code is written to capture what is
  found in each database
• flexible (dis)aggregation
• alternatives specified for selected assumptions
• including macro closures
• presence/absence of unemployment
• other features with a proven track record

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General Structure

• The model code includes
• pre-programmed reports of simulation results
• repmacro.xls
• repmeso.xls
• error diagnostics -- pinpointing errors in the
  database and simulations
• SAM balancing program -- to remove minor
  imbalances exceeding some small cut-off
• aggregation code

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File Structure

• The major file segments are
• data and base run
• simulations
• reports
• The files used under 1 and 2 differ depending on
  whether the core or MDG version of MAMS is used
• The main (.gms) file include other (.inc) files
  the same code is used in different places

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File Structure -- User Input
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Data and Base Run

• dmod.gms -- reads in data key include files
• ltappgt-data-general.xls the general database
• ltappgt-data-mdg.xls additional MDG database
• dmod2.gms (restart from dmod.gms) does the base
  run key include files
• diagnostics-data.inc (included in dmod2.gms)
  catches errors the database
• diagnostics-sol.inc (included in dmod2.gms)
  checks/debugs the base solution
• reploop.inc -- collects results from the base
  solution for reports

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Simulations

• dsim.gms (restart from dmod2.gms) runs
  simulations for analysis key include files
• ltappgt-sim-core.xls specifies non-base
  simulation assumptions/parameters (for core
  version)
• ltappgt-sim-mdg. xls -- specifies non-base
  simulation assumptions/parameters (for MDG
  version)
• reploop.inc collects results from the
  simulations for reports

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Reports

• drep.gms (restart from dsim.gms) processes raw
  simulation results key include files
• rep.inc (various include files) -- computes
  growth rates, GDP shares, defining standard
  tables, etc.
• repmacro.gms (restart from drep.gms) produces
  standard macro tables, exported to the file
  repmacro.xls
• repmeso.gms (restart from repmacro.gms)
  produces standard meso tables, exported to the
  file repmeso.xls

11
Alternative Model Versions and their Data Needs

• Core version
• uses ltappgt-data-general.xls and
  ltappgt-sim-core.xls does not use
  ltappgt-data-mdg.xls and ltappgt-sim-mdg.xls
• does not include the MDGs and their links to the
  labor market
• minimum recommended disaggregation
• factors labor, private capital, government
  capital
• sectors (activities/commodities) private,
  government
• institutions household, government, row

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Alternative Model Versions and their Data Needs

• MDG version
• uses ltappgt-data-general.xls, ltappgt-data-mdg.xls,
  and ltappgt-sim-mdg.xls does not use
  ltappgt-sim-core.xls
• covers MDGs and their links to the labor market
• minimum recommended disaggregation
• factors labor (by educational level), private
  capital, government capital (by function three
  education, health, water-sanitation, other
  infrastructure, other government)
• sectors (activities/Commodities) private,
  government (by function)
• institutions household, government, row