Simpson's paradox: a demographic case study of population dynamics, poverty, and inequality.

Brazil is undergoing a demographic transition characterized by regional inequalities. It is reasonable to assume that aspects related to poverty, development and inequality might reverse the sign of the association of indicators of demographic transition, exemplifying a phenomenon known as Simpson's Paradox. The aim of this study was to analyze the effect of inequality, poverty and social development on population dynamics in Brazil, verifying the occurrence of Simpson's paradox in demographic transition. We used population data from the 1991, 2000 and 2010 national censuses, broken down by age and federative unit (FU). The correlation between demographic indicators was assessed by stratifying the FUs into groups according to their median social indicators. The findings show that all FUs have progressed against social indicators and are undergoing demographic transition; however, despite reductions in disparities over the study period, persistent gaps exist between regions. Simpson's paradox was present when the analysis was carried out by census year and social indicators, and was particularly pronounced in 1991. The main challenge is to define how to analyze demographic dynamics in Brazil and understand how contextual factors alter the pace, quantum, and pattern of demographic transition.