Population dynamics drive much of what happens in the world from geopolitics to economic development. As such it is worthwhile having a broad appreciation of those dynamics. As a first step this article will explore estimates of global population from 1800 to 2100.
The first stop is to consider the excellent data set provided by the UN Population Division that produced its latest world population prospects for 2019.
The UN provides estimates of population by country per year from 1950 to 2020. This data shows that over this period total world population has more than tripled from just over 2.5 billion in 1950 to close to 8 billion in 2020.
From this view it looks like population has grown at a constant rate since the 1970s. However, if we look at annual changes we can see that whilst total population has indeed grown by around 80 million people per year there was a peak in population growth in the late 80s reaching an increase of nearly 93 million in 1988. Meanwhile on a percentage basis, population increase peaked at close to 2.1% per year in the late 1960s but has since slowly declined to an increase of just over 1% per year in current times.
Projecting forward to 2100 the UN provides 9 forecasts based on different scenarios. These 9 scenarios consider 3 key variables the first being fertility rate, the second being mortality rate and the third being migration rates. This is useful for assessing the impact that these variables have on population rates. In addition, the UN provides probabilistic forecasts that reflect the uncertainties in the projections based on historical variability in each of the variables. These projections are then based on several thousand distinct trajectories of each demographic component to derive estimates changes over time and probabilistic bands.
Unfortunately the UN only provides probabilistic estimates every 5 years. To provide an annual forecast I have taken the median, and 80% probability cases and used linear interpolation to estimate population on an annual basis.
Unfortunately the UN data does not provide information further back than 1950. Fortunately the UN did issue a report on “The World at Six Billion” from which it is possible to make some broad estimates of world population back to 1750. Interestingly at the time this report was issued (1999) the UN was estimating a global population of 8.91 billion in 2050 and 9.46 billion in 2100.