Calculating the Gallagher Index

The Gallagher Index measures how unfair a voting system is.

It looks at how we voted.
It looks at how we're represented.
Then it says how different those two measurements are.

So if a party gets more seats than votes, the index is high.
If all parties win seats in proportion to their votes, the index is zero.

Breaking it down

The following is how we calculate the Gallagher Index for Canada's 2015 federal election.

Votes Seats Vote % Seat % Difference Squared
{{ party.name }}
Sum
Halved
Square rooted

Resulting Gallagher Index
— {{ Math.round(gallagherIndex) }}% —

Maximum recommended by the Special Committee
— 5% —