Population ageing

Population ageing is an overall change in the ages of a population. This can typically be summarised in a single parameter as an increase in the median age. Causes are a long-term decline in fertility rates and a decline in mortality rates. Most countries now have declining mortality rates and an ageing population: trends that emerged first in developed countries but are now also seen in virtually all developing countries. In most developed countries, population ageing started in the late 19th century. By the late 20th century, the world population as a whole was also ageing. The proportion of people aged 65 and above accounts for 6% of the total population. This reflects a historic overall decline in the world's average fertility rate. That is the case for every country in the world except the 18 countries designated as "demographic outliers" by the United Nations. The aged population is currently at its highest level in human history. The UN projects that the population will age faster in the 21st century than in the 20th. The number of people aged 60 years and over has tripled since 1950; it 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. 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 respond to its implications. Policy interventions include preventative strategies that increase the size of the young, working-age population, as well as adaptive measures to make overarching systems compatible with a new demographic future.