Models of the future

Existing world models are criticized for the omission of feedback effects. Modifications to existing models are considered implausible, and a very simple structure representing the system by stocks and flows of energy is proposed. The planning implications of such simple models are explored in terms of risk evaluation. The analysis of a possible risk situation yields a dimensionless quantity relating capital investment, depletion rate, investment fraction and efficiency. This quantity is shown to be critical in determining the existence of discontinuities in the growth curve, independent of the desired level of growth.