In microeconomic models, money and prices are manipulated from outside the system determining part of the outcome. In PRICES (Figure IV-12a) the model determines the prices of goods produced. Economic models, which determine their own pattern from inside the system, are called macroeconomic models. This macroeconomic system is examined by letting autocatalytic growth generate economic assets (Q) with 3 pathways, one using fuels and minerals, and two based only on renewable resources. Renewable (J) and nonrenewable (F) sources drive production (P) of assets (Q) as in the 2SOURCE model (II-4).

Money is shown circulating in proportion to the money supply (M), and prices are the ratio of the two (money circulation (gross national product) divided by production (P)). In other words, this model makes money and prices (and their buying power) entirely dependent on real production and assets operating within the system.

In the simulation (Figure IV-12b) an index of prices (PR), which is production per dollar, is graphed, showing that prices tend to reach a minimum when production rate is highest, which comes before assets turn down. Then, as nonrenewable sources are used up, prices go up, showing inflation (less assets per dollar). Productivity (P) is also graphed, showing a maximum when assets and nonrenewable resources (F) are both moderately high. In recent years real prices of fuels, electricity and dependent commodities reached their minimum with highest productivities about 1972. In the simulation shown, money supply (M) is held constant, unlike the real system, which has been adding money supply each year.

Examples of Macroeconomic Models like BUYPOWER

This is a model for any country that is dependent on its own fuels and renewable resources and not very dependent on imports and exports. The Soviet Union fits this model. Even though the US has more trade, this can also represent our economy.

"What If" Experimental Problems

1. What happens to prices if the system starts with more fuel? Make F = 150, run and see.
   


2. If the system converts fuels more efficiently, how will that affect assets and prices? Increase K3 to 0.006.
   


3. How does the system react if it finds a way to use its renewable energies more efficiently? Increase K4 to 0.08.

COMPUTER MINIMODELS AND SIMULATION EXERCISES FOR SCIENCE AND SOCIAL STUDIES

Howard T. Odum* and Elisabeth C. Odum+
* Dept. of Environmental Engineering Sciences, UF
+ Santa Fe Community College, Gainesville

Center for Environmental Policy, 424 Black Hall
University of Florida, Gainesville, FL, 32611
Copyright 1994

Autorização concedida gentilmente pelos autores para publicação na Internet
Laboratório de Engenharia Ecológica e Informática Aplicada - LEIA - Unicamp
Enrique Ortega
Mileine Furlanetti de Lima Zanghetin
Campinas, SP, 20 de julho de 2007