One out of five Europeans, but one out of twenty Africans, is 60 years or older. In some developed countries today, the proportion of older persons is close to one in five. During the first half of the 21 st century that proportion will reach one in four and in some countries one in two. As the tempo of ageing in developing countries is more rapid than in developed countries, developing countries will have less time than the developed countries to adapt to the consequences of population ageing. By 2025 this is expected to climb to 62 percent of older persons, although large differences exist between more and less developed regions.
Large differences exist between countries, however.
Between 2000 and 2050, the old-age dependency ratio will double in more developed regions and triple in less developed regions. The potential socioeconomic impact on society that may result from an increasing old-age dependency ratio is an area of growing research and public debate.