These are some of the questions that readers of The Guardian recently asked Africa Check to look into.
What is Africa’s current population?
Current estimates suggest there were about 1.13-billion people on the continent in 2014. Data compiled by the United Nations Population Fund (UNFPA) puts Africa’s population at 1.132 billion, in line with the US Population Reference Bureau (PRB) figure of 1.136 billion and the World Bank’s estimate of 1.13 billion (excluding Western Sahara).
What is the continent’s projected population?
Projections for 2025 range from 1.397 billion to 1.486 billion. By 2050, the number of people in Africa is expected to increase by another billion and by 2100 the United Nations forecasts there will be 4.185 billion people on the continent. These projections – referred to as “medium variants” – are regarded as the most probable.
Statisticians also calculate “low” and “high variants”. The United Nations, for example, predicts Africa’s population could be as low as 2.826 billion by 2100, or as high as 6.007 billion. If fertility rates – based on data from 2005 to 2010 – remain constant, Africa’s population could grow to a staggering 17.221 billion.
How is future population size determined?
“Population projections are an educated guessing game,” says Diego Iturralde, manager for demographic analysis at Statistics South Africa. Projections are modelled on current population figures, migration data, mortality figures and fertility rates.
National census figures and health and demographic surveys – which provide fertility, mortality and migration data – are taken into account along with historical data on births, deaths and migration. Using this data, population estimates are calculated for every country in Africa and the estimates are then aggregated for the continent.
It is important to note that census figures for many African countries are not accurate. In some instances, current population estimates are based on old census data and are little more than projections themselves.
Fertility, mortality & migration’s influence
Fertility. In Africa, the fertility rate of countries has a major impact on projected population increases. The ten countries with the highest fertility rates in the world are located on the continent.
According to Anne Goujon, a researcher with the International Institute for Applied Systems Analysis (IIASA), countries with very high fertility rates – like Zambia, Nigeria and Niger – pose a significant challenge when it comes to predicting future population size.
“For sure, [fertility rates] will decline, but the speed of this decline is uncertain, and in terms of population projections, it makes a large difference in the result,” she said.
Mortality. People in Africa have the lowest average life expectancy in the world. The United Nations attributes this to a variety of factors, including the HIV/AIDS pandemic, tuberculosis and malaria whose long-term impact on population growth is difficult to predict accurately.
Migration is the single-most difficult component of population changes to measure reliably, the UN says.
Education. Unlike the UN, the IIASA also considers the impact of education on population growth. Research compiled by the Institute shows that women tend to have fewer children the more educated they are.
How accurate are these forecasts?
While population projections are certainly educated guesses, they can be surprisingly accurate. An evaluation of a series of United Nations population projections between the 1950s and 1990s found that all but one had a margin of error of less than 4%.
In Africa, however, the quality of data can pose significant problems. “Some [African] countries have very few censuses, and a number of censuses are of doubtful accuracy,” Professor Rob Dorrington, Professor of Actuarial Science at the University of Cape Town, told Africa Check.
Countries like Eritrea, South Sudan and the Democratic Republic of the Congo did not conduct population censuses between 2005 and 2014, as required by the UN for their 2010 round of projections. This year, Angola conducted its first national census in 30 years, Dr Mady Biaye, Technical Advisor for East and Southern Africa at the United Nations Population Fund, told Africa Check.
In Nigeria, the country’s census figures have been the subject of controversy for decades. Accusations of rigging date back to the 1950s and have continued unabated under military and civilian regimes.
According to Biaye, a number of factors – from unrest and conflict to the enormous cost of conducting a census – can also stand in the way. Depending on the means and technology used it can cost $1 or more than $2 for every person counted in a national census.
National civil registration systems in many African countries are weak and many do not accurately register births and deaths.
And time plays a role too. “The more years a projection covers, the greater the chance that unforeseen developments will produce unexpected changes in fertility, mortality, or migration,” Professor Nico Keilman, a demographer from the University of Oslo in Norway, wrote in a study on the accuracy of UN population forecasts.
Why population forecasts can be useful
Given all the variables, population forecasts – particularly long-range ones – should not be seen as cast in stone, but rather as useful guides.
The central projection by the United Nations that the population of Africa will grow to 1.467-billion by 2025, add a further billion by 2050 and climb to 4.185-billion by 2100 is just that, a projection, or as Statistics South Africa’s Diego Iturralde would have it, an “educated guessing game”.
Nevertheless, such projections, though uncertain, are still useful.
Iturralde argues that “the big[ger] picture is that the numbers must be used to inform what we can expect and what to plan [for].” As Biaye explains: “Populations will continue to grow. Every single person at every level of decision-making should be planning for that.”
Says the IIASA’s Anne Goujon: “In short, the long-range projections do not predict the future, they show different futures with some indication as to how to attain or avoid them.” – 22/10/2014
Edited by Anim van Wyk