Conciliating Absolute and Relative Poverty: Income Poverty Measurement Beyond Sen’s Model

The properties of poverty measures based on absolute poverty lines are well-known. Their prop- erties have been extensively studied in the model proposed by Sen (1976). In contrast, the properties of relativist poverty measures – measures based on non-absolute poverty lines – have never been rigorously studied. This is not merely a theoretical issue: relativist measures do provide highly de- batable poverty comparisons. This becomes increasingly problematic as relativist poverty measures are more and more used by policy makers. This paper proposes an extension of Sen’s model designed for the study of relativist poverty measures. Several results show that classical properties have dif- ferent implications in the extended model and in Sen’s model. Finally, the paper characterizes an index specifically designed for non-absolute poverty lines (Decerf, 2015). This result provides the first characterization of a relativist poverty measure.