Partisan symmetry, swing, competitiveness and disproportionality

PartisanGerrymanderMeasures: efficiency gap (Stephanopoulos and McGhee 2015; winners waste votes above half the district total), mean-median difference (McDonald and Best 2015) and uniform-swing partisan bias. ElectoralSwing: Butler and Steed swing. DistrictCompetitiveness: two-party margins and districts within threshold of a tie. Disproportionality: Loosemore-Hanby, Gallagher least squares and Laakso-Taagepera effective numbers of parties. Malapportionment: Samuels and Snyder (2001) MAL. Identical to the Python arm morie.fn.electgeo.

Usage

PartisanGerrymanderMeasures(votes_a, votes_b)

ElectoralSwing(prev_a, prev_b, cur_a, cur_b)

DistrictCompetitiveness(votes_a, votes_b, threshold = 0.05)

Disproportionality(votes, seats)

Malapportionment(seats, population)

Arguments

votes_a, votes_b

Two-party votes by district.

prev_a, prev_b, cur_a, cur_b

Vote shares in two elections.

threshold

Distance from 0.5 counted as competitive.

votes, seats

Party votes and seats.

population

Unit populations.

Value

List.

References

Stephanopoulos, N. O. and McGhee, E. M. (2015). Partisan gerrymandering and the efficiency gap. University of Chicago Law Review 82, 831-900.

Gallagher, M. (1991). Proportionality, disproportionality and electoral systems. Electoral Studies 10, 33-51.

Samuels, D. and Snyder, R. (2001). The value of a vote: malapportionment in comparative perspective. British Journal of Political Science 31, 651-671.

Examples

PartisanGerrymanderMeasures(c(70, 70, 40, 40, 40), c(30, 30, 60, 60, 60))$efficiency_gap
#> [1] 0.14
Disproportionality(c(40, 35, 25), c(55, 40, 5))$gallagher
#> [1] 18.02776