 This negative association between human fertility and socio-economic development has been “one of the most solidly established and generally accepted empirical regularities in the social sciences”.The researchers used cross-sectional and longitudinal analyses to examine the relationship between total fertility rate (TFR) and the human development index (HDI).The main finding of the study was that, in highly developed countries with an HDI above 0.9, further development halts the declining fertility rates.