DOI
N/A

Summary
In chapter 2 the main mathematical principle behind the World 3 model is presented: exponential growth. It is exemplified with population and productive capital as motors behind the exponential growth of food production and materials and energy use. The discussion on population growth is based on the demographic transition model and it´s description of consequences for growth by changes in birth and death rates. A number of countries for which demographic data exists are compared as regards their transitions up to year 2000 (in the original version this was up to 1970). Next the chapter turns to World Industrial Growth with a model of how Industrial capital (actual hardware such as machines and factories) provide outputs for three other groups of capital: Resource Obtaining (mining etc), Agricultural (irrigation, tractors etc) and Service Capital (schools, hospitals etc), and, further to consumer goods and to Industrial investments which is a feedback loop as input to the Industrial capital. The assumption is the made, and described in model terms, that more population will lead to poverty which in turn leads to higher population growth. This is illustrated by visualizations of total food production versus food production per capita for different world regions. The conclusion of the chapter is that birth and deathrates in combination with investments and depreciation rates determines the rate of the exponential growth, and in turn the consequences for the planet.

Relevance for Complex Systems Knowledge
The World 3 system’s feedback loops are presented and their probable effects on population growth. This is combined with explanation on the functioning of positive and negative feedback. Feedback loops related to Industrial capital are also presented and discussed. The combination of how these feedback loops impact on exponential growth is discussed, given assumption on what would drive positive or negative loops to take overhand.

Point of Strength
In chapter 3 the discussion focus on possible results of the system dynamics model. The discussion is is open as regards different types of uncertainties, relating to uncertainties in the model and to the availability of data and facts from the real world. Uncertainties regarding positive and negative feedback loops is discussed in relation to climate change. The discussion on possible scenarios include ethical dimensions for decision making based on the overview of scenarios.