The UN recently reported that the world's population reached 8 billion on 15 November, and much of this growth is attributed to longer life expectancy.
However, the UN predicts that in the next century, humanity will begin to decline due to aging and smaller societies.
This will pose a significant problem for countries that are already experiencing declining populations.
The reasons for declining populations vary from country to country, with some experiencing lower fertility rates, an aging workforce and low levels of immigration.
This is a problem that countries such as Japan, Italy and South Korea have been grappling with for many years.
While some experts argue that population decline can lead to economic opportunities, such as higher productivity and more innovation, others warn that it could lead to reduced consumer demand and an increased burden on social welfare programs.
Countries will have to take proactive measures to combat declining populations, such as increasing immigration and incentivizing people to have more children.
As Stuart Gietel-Basten, a professor of social science and public policy at the Hong Kong University of Science and Technology, notes: "It is not a quick fix to say 'just boost [the] fertility rate.
' It is a very difficult thing to do."