Human fertility declines with higher population density

Wolfgang Lutz, International Institute for Applied Systems Analysis (IIASA)
Maria Rita Testa, Vienna Institute of Demography
Dustin Penn, Austrian Academy of Sciences

Reproduction has been found to decline with increasing population density in a wide variety of species, yet demographers have not given systematic attention to density as a relevant factor in human reproduction. If human fertility also depends on population density, this has important implications for population projections, which conventionally ignore heterogeneity and assume universal convergence of fertility rates. We examine the relationship between population density and fertility in 145 countries since 1960, by using cross-sectional and time-series regression models controlling for some important social and economic variables. In all models we find strong and significant negative associations between density and fertility. In addition, we find that fertility preferences (ideal family size) decline with higher density across 54 regions of Europe. Our findings alter the way we think about future fertility and human population growth.