All this week we've been reporting on overpopulation. The United Nations predicts that by 2050, the world's population will be 50 per cent higher than it is today - nine thousand million people.
On Monday Nils Blythe reported from India, where the population is booming and last night he was in one of the world's biggest cities Mumbai.
Tonight, we heard from a country which in contrast to India, strictly controls its population: China.
In 1979 it introduced its one-child policy - now those first children born under the policy are grown up. Our Beijing correspondent James Reynolds told the story of the one child policy.
You can hear all THREE reports here:
TOMORROW night on PM we're going to debate population/overpopulation. Got a question or a point of view you want to express? Add your comment here.