The three-compartmental demographic model by Korotaeyv-Malkov-Khaltourina,
connecting population size, economic surplus, and educational level, is
considered from the point of view of dynamical systems theory. It is shown that
there exist two integrals of motion, which enable the system to be reduced to
one non-linear ordinary differential equation. The study of its structure
provides analytical criteria for the dominance ranges of the dynamics of
Malthus and Kremer. Additionally, the particular ranges of parameters enable
the derived general ordinary differential equations to be reduced to the models
of Gompertz and Thoularis-Wallace.Comment: 4 page