Proportional Representation, Gini Coefficients, and the Principle of Transfers

While various authors have appealed to Dalton's Principle of Transfers, the Lorenz curve, and the Gini Coefficient to assess disproportionality in proportional representation systems, some additional clarifications are warranted with regard to these concepts and their proper application to the disproportionality issue. This article shows that the three concepts keep their full power and internal consistency if one considers the proportional representation problem as one of maximizing equality of seat/vote ratios among individual voters. Inconsistencies arise if parties are taken as the relevant unit of account. If one insists on comparing parties, then the appropriate concern is rather with their `deviation from proportionality'. To assess that concept, measures of seat mobility are better suited than genuine inequality measures.