The ending of population growth when birth and death rates are equal. This would require an average number of 2.3 children per family. In 1993, 58 members of the World’s Scientific Academies stated that ‘there is no doubt that the threat to the [global] ecosystem is linked to population size and resource use…Family planning could bring more benefits to more people at less cost than any other single technology…Success in dealing with global social, economic and environmental problems cannot be achieved without a stable world population…We must achieve zero population growth within the lifetime of our children’ (1993, Royal Society, London). This is a contentious subject.