How Regions Shaped World Population Growth since 1960

World population has increased from approximately 3 billion in 1960 to almost 8 billion in 2020. While global population growth is significant, some countries are concerned about declining population trends within their borders. This blog post documents population shifts across various geographic regions.

The first figure illustrates the population in various regions of the world in 1960 and in 2020. While North American population increased from 199 million to 370 million, South Asian population increased from 508 million to 1.6 billion and sub-Saharan African population increased from 228 million to almost 1.2 billion.

The second figure illustrates the population change in terms of growth factor, defined as the ratio of 2020 population to 1960 population. World population grew by a factor of 2.6 over the past 60 years. South Asia grew by a factor of 3.2 and sub-Saharan Africa grew by a factor of 5.1. North America (1.9) and Europe and Central Asia (1.4) experienced much slower growth.

To help us determine how much each region contributed to the total global growth factor of 2.6, imagine that there were only two regions in the world: Region A and Region B. Denote the world population in 1960 as ${\text{PW}}_{\text{1960}}$ and the corresponding populations in the two regions as ${\text{PA}}_{\text{1960}}$ and ${\text{PB}}_{\text{1960}}$. Similarly, denote the 2020 populations as ${\text{PW}}_{\text{2020}}$, ${\text{PA}}_{\text{2020}}$, and ${\text{PB}}_{\text{2020}}$. In this example, ${\text{PW}}_{\text{2020}}={\text{PA}}_{\text{2020}}+{\text{PB}}_{\text{2020.}}$

Dividing both sides of the equation by ${\text{PW}}_{\text{1960}}$, we can see

so

The left-hand side of the above equation is the global growth factor over the past 60 years. The right-hand side is the weighted average of Region A’s and Region B’s growth factors. For instance, $\frac{{\text{PA}}_{\text{2020}}}{{\text{PA}}_{\text{1960}}}$ is Region A’s growth factor and $\frac{{\text{PA}}_{\text{1960}}}{{\text{PW}}_{\text{1960}}}$ is the population share of Region A in the world in 1960. We will refer to the product of the two terms —$\left(\frac{{\text{PA}}_{\text{2020}}}{{\text{PA}}_{\text{1960}}}\right)\left(\frac{{\text{PA}}_{\text{1960}}}{{\text{PW}}_{\text{1960}}}\right)$— as the weighted growth of A.

That is, the weighted growth of any region (e.g., Region A) is calculated as the region’s growth factor multiplied by its initial 1960 world population share.

The contribution of any region to the world population growth is its weighted growth divided by the global growth factor. In our example, Region A’s contribution is the weighted growth of A divided by $\frac{{\text{PW}}_{\text{2020}}}{{\text{PW}}_{\text{1960}}}$.

Using the above equation in our data, the contribution of each region is documented in the following table.

World population has increased by a factor of 2.6 over the past 60 years, but this growth has not been uniform across the world. While North America accounted for only 5% of the world population growth, South Asia accounted for 21% and the East Asia and Pacific region accounted for 30%.