Silly me; I thought world population now around 7 billion was going to stabilise at around 9 billion by 2050.
Not so according to the latest medium-variant projection by the United Nations . What they predict is that Africa’s population will continue to grow so that by century end the population will be nearly four times what it is now.
Well might you say that that would be impossible, the continent struggles to feed itself now. How could it possibly accommodate so many people? 
Population (in millions) according to the medium-variant projection
A famous population pessimist writing around 1800 was the Reverend Thomas Malthus. He got it wrong because he didn’t foresee the opening up of the New World and the dramatic reduction in transportation costs among other things. Nevertheless his basic thesis was right; population tends to grow faster than food production.
Of interest is that the population of Europe is expected to fall by 2050, continuing on to 2100. Asia falls after 2050.
It’s important that we look at this in terms of annual percentage changes. The table below is based on the above but with the first column showing the rate of change since 2000.
These numbers might look low but please remember that 2% pa means near 25% overall over 10 years. The African 1.1% over 50 years means a growth of 77%.
The countries with the highest rates of growth from 2000 to 2015 are (% pa):
And those with the lowest are:
Australia’s was 1.5% pa. This has been the subject of much debate. Do you remember Kevin Rudd’s famous Big Australia statement?
The countries with populations of at least 100 million in 2015 are:
Some near 100 million with high growth rates are Ethiopia (99.4 million), Egypt (91.5 million) and Vietnam (93.4 million). Joining all of these by 2100 will be (current population shown):
All these are in Africa except Iraq. Please don’t ask what the populations are likely to be in 2100, it’s too depressing, but to give you a teaser, Congo will be 389 million and Zambia 105 million.
To reflect on the issue of Africa, Rwanda’s population in 2100 is expected to be
25.7 million or 975 people per sq km. This is a country that has a very high proportion of the population dependent on subsistence agriculture. Ku-ring-gai’s density is not much above this at 1,278 people per sq km.
Japan will drop off the list.
One wonders just how accurate current counts are. Advanced countries use censuses where each household must complete a form every five or ten years.
What happens in third world countries with many villages often difficult to access and with literacy issues; think New Guinea? Presumably there is a lot of estimation.
The following table provides much available detail for selected countries. The first one is Australia. We should be familiar with our own country.
The next two are our near neighbours to the north. Neither has been a source of migration pressure on Australia. Indonesia has an enormous population; Papua New Guinea’s has grown rapidly.
China is extremely important. On 29 October China announced a further relaxation of its one child policy, it will now be a two child policy. China has been a major source of migrants to Australia and that is likely to continue.
Uganda is included as a representative African country. One was tempted to say typical but there is enormous variation across the continent. Russia is interesting because of projected population falls.
The first observation is to reflect on just how small Australia’s population is compared to the other countries. As of 2015 it is less than 10% of Indonesia’s and less than 2% of China’s.
The next part of the table shows annual percentage change, firstly for 2000–15, and then for the remainder of the century. The latter is very much an average so also shown is the end position, i.e. the change in the last year of the century.
Australia grew at 1.5% to 2015 but by 2099–2100 this will be down to 0.3%. Is this believable?
All the other countries in the list will also have much lower rates of population growth by then, except Russia which is already in decline. This is caused by birth rates being less than death rates and net migration.
To maintain population, births per woman, needs to be above two. It’s not now in Australia which is what gave rise to Peter Costello’s baby bonus.
Look at the frightening figure for Uganda for 2010–15 – nearly six. The rate for China is expected to increase.
Life expectancy is high for Australia and is expected to increase, as will be the case for all the other countries shown. The Russian figures are low for what is essentially a European country.
This increase will be accompanied by significant increases in the aged population; in Australia’s case the 80+ rises from 4% of the total now to 14% in 2100. Hopefully there will be improvements in medicine, in particular a treatment for dementia, so that people in this age bracket will have some quality of life.
 World Population Prospects: Key Findings and Advance Tables (2015 revision) Working Paper ESA/P/WP.241, United Nations, Department of Economic and Social Affairs, Population Division
STEP member, Jim Wells, has provided this article on the outlook for future world population numbers.