A soft landing @ 10 billion?
Johannes M.V.A. Koelman
At what rate has the population of the world been growing, and what are the future prospects?
According to the classical Malthusian Growth Model the world population tends to grow exponentially (i.e. with a constant annual growth rate) until the planet will no longer be able to support the huge numbers. However, it is easy to see that a constant annual growth is not supported by historical data.
The following figures for historical (blue) and prognosed (green) World population estimates were taken from Wikipedia:
Year (AD) Estimated Population (millions)
| 600 | 203.0 |
| 700 | 208.5 |
| 800 | 222.0 |
| 900 | 233.0 |
| 1000 | 282.9 |
| 1100 | 315.3 |
| 1200 | 401.7 |
| 1300 | 398.0 |
| 1400 | 356.0 |
| 1500 | 452.5 |
| 1600 | 535.7 |
| 1650 | 507.5 |
| 1700 | 616.5 |
| 1750 | 760.2 |
| 1800 | 936.8 |
| 1850 | 1,238.4 |
| 1900 | 1,660.3 |
| 1910 | 1,750.0 |
| 1920 | 1,860.0 |
| 1930 | 2,070.0 |
| 1940 | 2,300.0 |
| 1950 | 2,494.0 |
| 1955 | 2,771.1 |
| 1960 | 2,995.4 |
| 1965 | 3,324.3 |
| 1970 | 3,696.4 |
| 1975 | 4,035.5 |
| 1980 | 4,459.0 |
| 1985 | 4,881.2 |
| 1990 | 5,260.8 |
| 1995 | 5,706.7 |
| 2000 | 6,064.0 |
| 2005 | 6,456.1 |
| 2010 | 6,824.4 |
| 2015 | 7,208.3 |
| 2020 | 7,654.5 |
| 2025 | 7,898.9 |
| 2030 | 8,143.1 |
| 2035 | 8,420.7 |
| 2040 | 8,631.6 |
| 2045 | 8,840.9 |
| 2050 | 9,059.4 |
When deriving annual growth rates from these figures, and plotting these as function of time, Figure 1 results. Prominent feature in this figure is the hyper-exponential growth resulting in annual growth percentages that have increased over recent centuries and seem to have exploded in the 20th century. It is because of pictures like these, that many believe that the population is growing at such a rate that in the near future some Malthusian catastrophe is bound to happen. This neo-Malthusian viewpoint, I believe, is not supported by the data.
The growth rate of the human population obviously does depend on time, but this dependency is an indirect one. One might expect a more direct dependency between the growth rate and total population. So, rather than plotting the annual growth rate as function of time, it is more insightful to plot this growth rate as function of total population. When doing so Figure 2 results.
The features stressed by this figure are markedly different from the Malthusian catastrophe feature prominent in Figure 1. In fact, as is evident from Figure 2, the global population growth rate has been steadily increasing proportional with the total population figure, until a peak annual growth rate slightly above 2% was observed when the global population reached the 4 billion mark. This happened in the early 1960s. Further growth beyond 4 billion resulted in a steady decline in the growth rate. Extrapolating the decline in growth rate, one might expect to reach a zero growth rate for a global population of about 10 billion.
Notice that the transition from increasing to decreasing growth rates occured more than four decades ago. No catastrophe was observed. Despite medical advances and massive increases in agricultural productivity both leading to a reduced mortality, we have made a global transition from hyperbolic growth (characterised by annual growth percentages increasing in proportion with the total population) to a declining growth trend that suggests a levelling-off of the total global population at around the 10 billion mark.
