60,000 



I 50,000 

 o 



i 40,000 



rts 



S 30,000 



i- 



C3 



^ 20,000 . 



o 



^ 10,000 

 o 





1950 1955 1960 1965 1970 1975 1980 

 TIME, yr 



Figure 4. Coal equivalent calories per dollar of gross 

 national product per year. 



collected, because the cost of energy has been increasing steadily in recent 

 years. 



ENERGETICS MODELING METHODS 



Step procedures for developing energetics models of socioeconomic and 

 environmental systems are described in this section. 



STEP 1: ECOLOGICAL SYSTEMS MAPPING 



The important first step in the design of an energetics model is the 

 identification of all principal natural and man-made systems. Each vegetative 



285 



