The Sen Index (also S-Index or S-Measure) is a poverty measure that was introduced by the economist Amartya Sen in the 1970s. The measure was novel in two ways. First, it integrated issues of relative deprivation and inequality into statistical poverty analysis. Second, it was based on a number of axioms or prerequisites that a meaningful poverty measure had to fulfill. Before the presentation of the Sen Index, poverty measurement had rarely been the subject of thorough methodological study. Usually, the poor had been identified by means of a poverty line, but an index that combined all available information on the poor did not exist. The lasting legacy of the Sen Index is that it prompted the emergence of poverty measurement as a distinct and ...