After loading all the input data files in the C:\PELPS\GFPM subdirectory. You can launch the GFPM by clicking the GFPM icon or by typing GFPM at the C:\PELPS\GFPM\ prompt. This brings up the GFPM main menu (Figure 3).
Figure 3. The main menu of the GFPM model
Because of the hierarchical structure of the GFPM, the steps from "1) Create input files" to "5) Get output", must be executed for the WORLD model before any regional model.
The six options have the following functions.
This option breaks the master input files into a set of working files. This operation has no visible output, and lasts about half a minute. This step needs to be executed only after constructing or loading a new master input file for the first time.
For users of Windows NT, this option brings-up the menu shown in Figure 4 and users can create the input files for a model by clicking a save button of the appropriate name in the menu. Users of Windows 95 must access the menu shown in Figure 4 manually, before selecting option 1 in the GFPM menu. This is done by opening the file C:\PELPS\GFPM\INPUT.XLS and clicking on the save button(s) of the appropriate name(s) to save input data set(s) as described above.
Figure 4. The save input menu
This option allows a choice of three run-time parameters of PELPS: solution range, number of steps, and projection length. T current version of the GFPM has already defined the run-time parameters which do not need to be changed. In order to run new versions of the GFPM, the parameters are described below:
Solution Range: This parameter controls the range (in quantity) over which supply and demand curves are approximated in stepwise manner. For a given number of steps, a larger solution range decreases the precision of the stepwise approximation, but reduces the chance that a solution will lie outside the range of the stepwise approximation, where the curves are flat (Zhang et al. 1993). In the GFPM, the default solution range is 0.10, i.e. ±10% around the previous year's equilibrium quantity.
Number of Steps: This parameter defines the number of steps in the linear approximation of demand and supply curves. There is a trade-off between precision and model size. More steps increase precision, but also increase the likelihood of memory failure. the GFPM is set to 12 steps for the world model and 6 steps for the regional models, high enough for adequate precision.
Projection Length: The default projection length of the GFPM is 16 years, but may be changed.
This option solves for equilibrium prices and quantities (production, consumption, imports and exports) by country and commodity in the base year only. Running the base-period provides a way to check whether the model solution replicates observed market outcomes in the base year with reasonable accuracy (see Appendix C on calibration).
Option 4 prompts the GFPM to project production, consumption, imports, exports and price by country and commodity over the number of years specified in Option 2.
For Windows NT users, choosing this option will automatically produce the Get Output menu (Figure 5). Windows 95 users must generate the Get Output menu manually, by opening the file C:\PELPS\GFPM\OUTPUT.XLS.
Figure 5. The get output menu
After running a model, the model's results can be organized and placed in the C:\PELPS\PELPS\OUTPUT directory by clicking the corresponding button in the above spreadsheet, e.g., by clicking "GetAmerica" after running the "AMERICA" regional model. However, in order to avoid overwriting old files, the OUTPUT directory can be renamed, but the user must create another directory named OUTPUT for the subsequent run.
After running the WORLD model and clicking the "GetWorld" button, the user can click the "AnalyzeWorldModel" button to produce the file C:\PELPS\GFPM\TREND.XLS, which shows the historical and projected trend of consumption and net trade for the four regions in the WORLD model (Africa, America, Asia, and Europe).
To link the regional models to the WORLD model, click the "LinkGfpm" button after running the WORLD model and before running a regional model (for details, see Appendix G: Linking the WORLD and regional models).
Results for each regional model are in seven files: consumption, production, imports, exports, net trade, capacity, and prices. These files include numerical and graphical results, and they are initially placed into the C:\PELPS\PELPS\OUTPUT directory. These files are useful to judge the results of a regional model, before proceeding to another region.
The raw country tables for the whole GFPM model (i.e. which include the results for all the commodities and countries in one sheet), are in the "output" sheet in C:\PELPS\GFPM\OUTPUT.XLS. This can be updated as the model is re-run region by region by saving the OUTPUT.XLS file after retrieving the result for each regional model.
The final results of the GFPM are in file C:\PELPS\GFPM\SUMMARY.XLS. This file contains:
· Charts of projections (1995 to 2010) and past trends (1965 to 1994), for Asia, Africa, America, and Europe, as in Figure 6, 7.
· Tables of projections (2000 and 2010) and past data (1970, 1980, 1990, and 1994) for the world, Asia, Africa, America, and Europe, as in Table 11.
· Charts of real world prices, historical (1965 to 1994) and projected (1995 to 2010), as in Figure 8.
· Detailed table by commodity, country, and activity, observed (1980 and 1994), and projected (1995 to 2010), as in Table 12.
The historical data in OUTPUT.XLS and SUMMARY.XLS files is contained in hidden columns. This data has been copied from the FAOSTAT database. The data can be updated, but the format should be changed because the macros in the two workbooks are only designed for having the data in its current format.
This option allows you to exit the GFPM.
Figure 6. Example of graphical results in the GFPM model (consumption)
Figure 7. Example of graphical results in the GFPM model (net trade)
Figure 8. Example of graphical results in the GFPM model (real world price)
Table 11. Example of numerical results in the GFPM model (summary table)
Table 12. Example of numerical results for ASIA region in the GFPM model (detailed country table)