The theory of demographic (or ecological) cycles is one of the new trends in socio-economic history. A distinctive feature of this direction is the use of ecological models of population dynamics. The beginning of the theory of demographic cycles was laid by the American biologist and demographer Raymond Pearl, who proved that the change in population size is described by the so-called logistic equation 1 solution to this differential equation is the logistic curve (Fig. 1). The behavior of the logistic curve shows that at first, in conditions of abundant resources and high consumption, the population size increases rapidly. However, due to limited resources, this growth is accompanied by a decline in per capita consumption (consumption curve in Figure 1). In real history, we can observe a similar situation, for example, in Qing China; data from this time have been preserved that allow us to plot curves of population growth and consumption decline (Figure 2). The decline in consumption leads to a decrease in the number of population growth decelerates, and the population stabilizes near the asymptote corresponding to the maximum possible size with minimal consumption. This state of" starvation homeostasis "is actually unstable; in the absence of food supplies, a large crop failure sooner or later causes a" demographic catastrophe", a terrible famine accompanied by epidemics. A catastrophe means a sharp decline in the population; then a period of growth begins in a new demographic cycle. Thus, from the point of view of demography, the historical process is a sequence of demographic cycles. A mirror image of demographic cycles is cyclical changes in per capita consumption, i.e. cycles of real wages (Figure 3). The existence of demographic cycles in history was proved by Wilhelm Abel and Michael Postan in the 1930s. 2 After the work of these researchers, the cyclical theory became widely accepted; its presentation can be found in the works of well-known scientists, suc ... Read more