Human ageing is a global phenomenon, linking north, south, east and west. Indeed, while the more developed countries aged substantially in the last century, it is the less developed ones that will see the greatest and most rapid increase in the number of people aged 60 years and over during the first half of this century. The global increase in this age group will be from 10 per cent of the total population in 1998 to 21 per cent in 2050 (from around 600 to almost 2000 million) and, in the less developed countries, the absolute numbers are expected to quadruple.