Population conferences have evolved through three overlapping stages, each stage reflecting a different perspective on the relationship between national policy formulation and the international system. Initially, at Rome in 1954 and in Belgrade in 1965, participants were invited on the basis of their expertise and were not expected to represent their governments. By the time of the Bucharest Conference in 1974, the United Nations, in an attempt to give conferences a greater role in shaping population policy and to inspire member governments to show greater concern for their own population problems, decided that conferences would be intergovernmental gatherings and that national delegations would be selected by governments. The effect of this change was that governments gave less weight to scientific expertise and, conversely, greater weight to political and bureaucratic considerations. Conferences in the twenty-first century likely will be compelled to confront diverse demographic problems in addition to social issues demanding the attention of the political system at every level.