Population ageing

Population ageing is an increasing median age in a population because of 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 are now seen in virtually all developing countries. In most developed countries, the phenomenon of population aging began to gradually emerge in the late 19th century. The aging of the world population occurred in the late 20th century, with the proportion of people aged 65 and above accounting for 6% of the total population. This reflects the overall decline in the world's fertility rate at that time.^[1] That is the case for every country in the world except the 18 countries designated as "demographic outliers" by the United Nations.^{[2][failed verification]} The aged population is currently at its highest level in human history.^[3] The UN predicts the rate of population ageing in the 21st century will exceed that of the previous century.^[3] The number of people aged 60 years and over has tripled since 1950 and reached 600 million in 2000 and surpassed 700 million in 2006. It is projected that the combined senior and geriatric population will reach 2.1 billion by 2050.^[4][5] Countries vary significantly in terms of the degree and pace of ageing, and the UN expects populations that began ageing later will have less time to adapt to its implications.^[3]