Nevertheless, to support their claims, all the participants in population debate depend on data, provided by national and international agencies. Population censuses provide useful data on size and growth of population which are supplemented by estimates of demographic rates by international, national and sub-national surveys. Further, the World Population Conference, held in Bucharest in 1974, and subsequent international conferences on population too have influenced the perceptions and ideas of politicians, bureaucrats, academicians and NGOs, by raising new questions, sharing experiences, providing a platform to discuss and debate various issues, and presenting scientific analysis on population processes. Such conferences have led to paradigmatic shifts in the theory of population and approaches to family planning programmes. It may be added here that the consultants, academicians and media persons too play a role in population policy by providing data, perspectives and creating a public opinion favourable to population policy.