Figure 6 illustrates the case of France which can be modelled by two similar symmetrical cycles. In both cases, a 7 year time shift gave a good correlation. But almost all fail to see when the peak of production will be reached and to compute how much oil is needed until exhaustion to supply their scenarios. In a Hubbert curve as the ultimate is 0.8. It has become clear that many things besides oil can be modelled in the same way, for example population and climate.
National populations change over time.
It is the same with stars, the dinosaurs and eventually humans too. Population declines when the fertility rate of a country falls below 2.1 children per woman. There is a time lag because of the pyramid of age , but populations do peak and decline. The curves can be modelled in the same way as discussed above. According to Bourgeois-Pichat 1988, industrial populations will soon peak, to be followed by the developing countries some 40 years later as they try to emulate the industrial countries.