Rich countries worry about the old people they have to keep fed and watered, but half the world is still under 25, including one billion between 15 and 24. The population continues to soar in sub-Saharan Africa and parts of South Asia.

However, India, which passed the one-billion mark in 1999, has shown that poverty and over-population need not necessarily go hand in hand.

Good governments can make an enormous difference to the masses. Several states in India, such as Uttar Pradesh, Bihar and Rajasthan, are facing exploding populations, with women still expected to fulfil a traditional role as wives without considering the prospects for their children. Other Indian states have already reached the level where births merely replace deaths; Tamil Nadu, which has long stressed "self-respect", is almost there.

It may seem like a long road for the country. But if the country is determined to spend on educating the masses about the importance of birth control and at the same time change their perceptions on the role of women, population growth can be controlled.

China's population is young but, by 2020, more than 15 per cent of Chinese will be above 60 - similar to Japan's situation today but on a poorer economic base. Therefore, good population planning is vital for China before it gets out of control.