Prospects of world population decline in the near future: a short note

An article in Science (4 November 1960) proposed Friday 13 November AD 2026 as the "Doomsday" of planet Earth, a doomsday produced by the "world population" going to infinity. In that paper, a rudimentary rate equation describing the evolution of the world population with time, was approximated in such a way that a quantitative calculation produced that particular date. In this note, we give a more realistic rate equation which respects general conservation principles and we compare previous results and the results of our calculation, with actual UN data for 1960-2010 and UN medium term projections. At present there is disagreement among experts as to what can be expected for the world population in the future. Some think that the population is still growing out control, some say it will be approximating a constant level by 2050, whilst others expect it to be clearly in decline somewhere between 2050 and the end of 21st century. Our model shows conclusively that if no drastic and unexpected changes take place soon, the world population will be decreasing at an accelerated rate after 2050. Our rate equation approach is similar to that used in condensed matter physics and chemical physics to describe the evolution of a two level system under an external perturbation. The result is much more realistic than a purely exponential result as has been generally assumed in the last decades of the last century.