Principle of dynamic balance of demographic process and the limits of world population growth (Q6123101)

The paper proposes a dynamic population model in which the change in population over a period of time is represented by the accumulated births and deaths over the period (called `integral inflow' and `integral outflow'), using the common population balance equation. The accumulated births and deaths are then modelled and extrapolated thanks to their smooth change over time, and this is how the author arrives at his method of population projection. The model fits the most recent (2011--2021) data on world population growth well, thanks to the smooth change in world population and the ease of extrapolation over such short periods. Unfortunately, however, the model does not seem to offer any new insights or efficiency in projecting population into the future with considerable uncertainty in the components, especially in global fertility. The author's observation that cumulated deaths lag behind cumulated births, despite the attempt to present it in a formal-mathematical way, is only the current feature of population dynamics, thanks to long period of continuous population growth (and partly to decreasing mortality, i.e. `postponed' deaths). This feature could easily be reversed in the future if births begin a long decline.