By 2050 the number of older people will exceed the number of young people for the first time in history, the United Nations predicts. Here is an overview of our ageing world:

-- Falling birth rates and increasing longevity are driving a largely irreversible trend towards older populations, the UN Population Division says.

-- There were around 600 million older persons around the world as the twenty-first century began; three times the 1950 level. By 2050 the UN estimates the number will triple to 2 billion.

Oldest and youngest median ages

-- Yemen has the world's youngest population: median age 15.

-- Japan has the world's oldest population: median age 41.

-- Globally, the world's median age is 26 years. The UN predicts it will increase to 36 by 2050.

The older population is ageing, and female

-- The fastest growing age group is the over 80s. Currently increasing by 3.8 percent a year, by 2050 one fifth of older persons will be 80 years or older.

-- The majority of older persons are women, because of their higher life expectancy.

Regional disparity

-- In developed countries, almost a fifth of the population was 60 or older in 2000.

-- In developing countries only 8 percent are over 60.

-- In August 2006, China announced it had the world's largest ageing population with 143 million people aged over 60. Its National Working Commission on Ageing predicts the number will be more than 400 million by 2050.

(Reuters)