Gallagher index
Calculates the Gallagher index for an election result.
The Gallagher index measures an electoral system’s relative disproportionality between votes received and seats allotted in a legislature. As such, it measures the difference between the percentage of votes each party gets, and the percentage of seats each party gets in the resulting legislature -- and it measures this dis-proportionality from all parties collectively in one given election. This collective dis-proportionality from this one election is given a precise score, which can then be used in comparing various levels of proportionality among various elections from various electoral systems.
Use
var gallagher = ; var parties = name: 'Party A' votes: 1058636 seats: 59 name: 'Party B' votes: 614937 seats: 34 name: 'Party C' votes: 247372 seats: 14 name: 'Party D' votes: 147544 seats: 8 name: 'Party E' votes: 59237 seats: 0 name: 'Party F' votes: 31982 seats: 3 name: 'Party G' votes: 24168 seats: 1 name: 'Party H' votes: 23889 seats: 1 name: 'Party I' votes: 13443 seats: 1 name: 'Party J' votes: 11738 seats: 0 name: 'Party K' votes: 1714 seats: 0 name: 'Party L' votes: 1595 seats: 0 name: 'Party M' votes: 1209 seats: 0 ; var result = ; // 2.377974544114885