(Dis)proportionality Measures¶
The proportion
module contains functions for measuring
disproportionality in electoral systems.

voting.proportion.
adjusted_loosemore_hanby
(votes, seats, parties='votes')[source]¶ Calculate the adjusted LoosemoreHanby index of disproportionality.
\[N \sum_{i=1}^n v_i  s_i\]where N is \(\sum_{i=1}^n v_i\) if
parties == 'votes'
or \(\sum_{i=1}^n s_i\) ifparties == 'seats'
. Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts
parties (str) –
votes
orseats
to use to calculate the effective number of parties

voting.proportion.
dhondt
(votes, seats)[source]¶ Calculate the D’Hondt index of disproportionality.
\[\max \frac{s_i}{v_i}\] Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts

voting.proportion.
gallagher
(votes, seats)[source]¶ Calculate the Gallagher index of disproportionality.
\[\sqrt{\frac{1}{2} \sum_{i=1}^n (v_i  s_i)^2}\] Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts

voting.proportion.
grofman
(votes, seats, parties='votes')[source]¶ Calculate the Grofman index of disproportionality.
\[N \sum_{i=1}^n v_i  s_i\]where N is \(\sum_{i=1}^n v_i^2\) if
parties == 'votes'
or \(\sum_{i=1}^n s_i^2\) ifparties == 'seats'
. Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts
parties (str) –
votes
orseats
to use to calculate the effective number of parties

voting.proportion.
least_square
(votes, seats)[source]¶ Calculate the least squares index of disproportionality.
\[\sqrt{\sum_{i=1}^n (v_i  s_i)^2}\] Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts

voting.proportion.
lijphart
(votes, seats)[source]¶ Calculate the Lijphart index of disproportionality.
\[\max  v_i  s_i \] Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts

voting.proportion.
loosemore_hanby
(votes, seats)[source]¶ Calculate LoosemoreHanby index of disproportionality.
\[\frac{1}{2} \sum_{i=1}^n v_i  s_i\] Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts

voting.proportion.
rae
(votes, seats)[source]¶ Calculate Rae’s index of disproportionality.
\[\frac{1}{n} \sum_{i=1}^n v_i  s_i\] Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts

voting.proportion.
regression
(votes, seats)[source]¶ Calculate the regression index of disproportionality.
\[\frac{\sum_{i=1}^n v_i s_i}{\sum_{i=1}^n v_i^2}\] Parameters
votes (list) – a list of vote counts
seats (list) – a list of seat counts