Modeling the Dropof f Between Minority Populat ion Share and the Size of the Minority Electorate in Situations of Differential Voter Eligibility Across Groups*

In any consti tuency partitioned into two discrete and mutually exhaustive groups, the difference be tween a group's share of the eligible electorate and its share of the total population will depend, on the one hand, on the differences in the age structure and eligibility rates of the two groups and, on the other hand, it will also depend upon the relative population sizes of the two groups. We model the exact nature of this relationship, providing formulae which allow us to ascertain the maximum difference be tween a group's share of total population and its share of the eligible electorate and to specify the percentage for 'effective voting equality', i.e. the population proport ion in a consti tuency for a group whose members have lower rates of voter participation needed to equalize the sizes of each group's eligible electorate. We discuss the applicability of these results to remedial districting plans in black/Hispanic voting rights cases in the United States and their implications for the differential holding of identity papers among blacks and non-blacks in South Africa. Copyright © 1996 Elsevier Science Ltd.