A GLOBAL MODELING APPROACH TO THE MODELING OF WORLD FOREST PRODUCTS: A ONE-SECTOR
4 QUANTITATIVE ESTIMATIONS AND MODEL STRUCTURE
The model is based on econometric relationships connecting production and de- mand for pulp and paper products with factors describing the general level of economic development (e.g. the Gross Regional Product (GRP) per capita in the different regions),
Forest resources
FIGURE 4 The logical structure of the model.
the availability of natural resources, traditions in this branch of industry, international prices, etc. Linear multiple-regression equations are used in most cases, and all the esti- mations are performed on a per capita basis.
The following is an example of an equation used in the model:
where P t ~ f is the per capita production of pulp in region i at time t , G R P ~ is the per
Global modeling approach to world forest products 185 consumption of roundwood in region i at time t (it should be mentioned that round- wood and pulp consumption denote industrial rather than personal consumption).
More than 5 0 0 equations have been estimated using historical data for the period 1960-1 977; 160 ofathese were used t o construct the model, according t o the best statis- tical fit.
The following variables are treated exogenously in the model: (1) level of economic development in the regions, defined by GRP per capita (scenarios); (2) population in the regions (scenarios); (3) forest resources (to be endogenized subsequently).
The main endogenous variables in the model are (1) production and consumption of raw materials and pulp and paper products for each region; (2) trade flows between the regions; and (3) absolute and relative international prices of raw materials and pulp and paper products.
The model structure is presented in Figure 4. Logically it follows the sequence of the chemical processing of wood: roundwood, pulp, paper products. Structurally these blocks are identical: each consists of a production subsector, a demand subsector, a prices and trade subsector, and a consumption subsector. Three final commodities are specified in the paper products block: newsprint, printing and writing paper, and other paper and paperboard.
Model performance is based o n the equilibrium of the world market. The supply and demand of different products are defined separately for each region and each year.
The initial value of the international prices is also defined for each step using a trend function. Then the total world production and demand are determined and it is assumed that the existence of a difference A # 0 causes a deviation A p of the price from the trend value. A p in its turn causes changes in the value of production and demand in the regions.
The price for which A = 0 (or [A1
<
6 ) is taken as the international price. The regional demands corresponding to this price are taken as consumption; that is, the excesses of production over demand form a pool which is then distributed among the regions in which demand exceeds production. In cases where equilibrium cannot be reached during the period studied, the valued
over-(or under-)consumption AC is defined in each region;this value then influences demand in the following year. This logical structure made possible the creation of a dynamic simulation model which gives yearly results for the endogenous variables. The model parameters have been adjusted t o fit the historical trends from 1 9 6 4 to 1977.
5 RESULTS
Some preliminary results obtained with the model are presented in Tables 4-7.
Table 4 shows production and potential consumption of pulp in the seven regions till 1990. Tables 5 , 6 , and 7 show the figures for newsprint, printing and writing paper, and other paper and paperboard, respectively. Population forecasts have been taken from UN projections while the rates of growth of GRP per capita are based on Leontiefs study (Leontief, 1977). The results should be treated with caution as the model is still in the process of development.
186 R. Dobrinsky
TABLE 4 Model results for pulp (millions of tonnes).
- -
1980 1985 1990
Regiona Production Potential Production Potential Production Potential
demand demand demand
TABLE 5 Model results for newsprint (millions of tonnes).
Regiona Production Potential Production Potential Production Potential
demand demand demand
TABLE 6 Model results for printing and writing paper (millions of tonnes).
1980 1985 1990
Regiona Production Potential Production Potential Production Potential
demand demand demand
Global modeling approach t o world forest products
TABLE 7 Model results for other paper and paperboard (millions of tomes).
Production Potential
In the last few years global modeling activities have shown a trend toward dealing with practical problems. In our study we have tried to apply the global modeling approach t o the modeling of one sector of world industry. A future objective in our studies will be the linking of the global model with a national model of the same sector. The global model will feed the national one with data about world prices, trade flows, and demand patterns and thus will be one of the tools for planning the future development of this sector of the national economy.
REFERENCES
Hafele, W. and Basile, P. (1979). Modeling of Long-Range Energy Strategies with a Global Perspective.
Operational Research '78. North-Holland, Amsterdam.
de Hoogh, J., Keyzer, M., Linnemann, H., and Van Heemst, H.D.J. (1975). Food for a growing world population. In G. Bruckmann (Editor), MOlRA: Food and Agriculture Model. CP-77-1. Inter- national Institute for Applied Systems Analysis, Laxenburg, Austria.
Leontief, V. (1977). The Future of World Economy. United Nations, New York.
Moiseev, N. (1977). Un systkme de simulation homme-machine pour les Ctudes globales des dCs5qui- libres thermiques. In the Proceedings of the World Conference, "Towards a Plan of Action for Mankind", Vol. 4. Pergamon, Oxford.
Panov, 0. (1978). Global modeling and social management. New trends in mathematical modeling. In the Proceedings of an International Seminar o n Trends in Mathematical Modeling, 2nd, lablona, December 1974. Ossolineum, Wrodaw.
Panov, 0 . and Dobrinsky, R. (1979). Global Modeling and the Management Problem. Institute of Social Management, Sofia. (In Bulgarian.)
Persson, P. (1974). World Forest Resources. Review of World Forest Resources in the Early 70s.
Skogshogskolan, Stockholm.
Persson, P. (1977). Scope and Approach t o the World Forest Resources Appraisal. Skogshogskolan, Stockholm.
Richardson, J . (1978). Global modeling. Futures, 10 (5,6).
188 R . Dobrinsky
DISCUSSION
Asked by Parker how trade is represented in the model Dobrinsky replied that it is simply the difference between production and demand in any one region, independent o f prices - "region" in this case meaning a part of a countly and not a group of nations.