Population ageing

Population ageing is an increasing median age in a population due to declining fertility rates and rising life expectancy. Most countries have rising life expectancy and an ageing population (trends that emerged first in developed countries, but which are now seen in virtually all developing countries). This is the case for every country in the world except the 18 countries designated as "demographic outliers" by the UN. The aged population is currently at its highest level in human history.

This has led to the rise of emergent countries with a large chunk of their population being in the working-age, while more developed countries run out of it, thus, becoming stagnant. Examples of those countries are the ones in Africa and South Asia.