Journal Article Historical Article 3,622 Biography 1,065 Population 568 Demographic Factors 540 Population Dynamics 481 Developing Countries 368 Economic Factors 332 Research Methodology 322 Research Support, Non-U.S. Gov't 268 Developed Countries 266 Population Characteristics 263 Socioeconomic Factors 243 Fertility 174 Americas 172 Asia 172 Migration 160 North America 147 Portrait 146 Genetics and Reproduction 137 Mortality 131 Research Support, U.S. Gov't, Non-P.H.S. 130 Models, Theoretical 129 Geographic Factors 127 Northern America 126 Socioeconomic Status 125 Age Factors 121 Studies 116 Africa 114 United States 112