This paper attempts three tasks: First, an overview of some of the kinds of overshoot and collapse models that have been proposed. Second, qualitative speculation on properties of homo sapiens that might make us either prone to collapse or to make collapse unlikely. This review aims to address whether the models have identified the key variables and relationships of the human population/economic system by attempting to connect ecosystems, the real economy and the financial economy. The latter deserves attention due to the dramatic collapse in world financial markets in 2008. A third aim is to propose features of a world population/economic forecasting model that would correct some of the deficiencies of earlier models. Methods include presentation of several system dynamics models implemented with ISEE software.
Results/Conclusions
Probably the most well known system dynamics model, presented in The Limits to Growth (Meadows, Meadows and Randers, 1972), predicted a collapse of human population during the 21st century. That model attracted strong criticism from economists, who pointed out that it did not incorporate technological innovation or substitution of inputs in response to price signals. Several subsequent authors (e.g. Catton, 1980, the Ehrlichs (several titles), Kummerow, 1999, Taylor, 2009, Good, 2009) have proposed overshoot and collapse models or scenarios. A more comprehensive and defensible model structure introduces major areas of uncertainty and areas for intentional policy. Two important conclusions are possible based on this kind of integrated model: First, outcomes are inherently uncertain and highly dependent upon human decisions. Second, that booms lead to busts—the higher population goes, the farther it will have to fall.
