Wolfgang Lutz|Qiang Ren
Determinants of human population growth
International Institute for Applied Systems Analysis|International Institute for Applied Systems Analysis
20th century seen unprecedented growth human population planet beginning century earth estimated 16 billion inhabitants number grew 61 billion end century significant growth near certainty paper tries summarize factors lie behind extraordinary expansion human population population growth expect future discusses concept demographic transition preconditions lasting secular fertility decline recent fertility declines parts world make likely human population growth come end course century parts developing world significant population growth still expected coming decades slowing population growth declining birth rates together still increasing life expectancy result strong ageing population age structure finally paper presents global level systematic analysis relationship population density one hand growth fertility rates analysis indicates addition wellstudied social economic determinants population density also presents significant factor levels trends human birth rates