Gerrymandering Optimization : An Assessment of the Possibility of Gerrymandering in Swedish Municipal Elections

Sammanfattning: This study examined possibilities of preforming gerrymandering within Swedish municipal elections before 2015, when new regulations contributing to guaranteeing a proportional seat allocation and thereby eliminating the risk of gerrymandering altogether were introduced. As the configuration of the districting problems in Swedish elections follows that of spatial unit allocation, these problems could be modelled as integer-programming problems including previously formulated constraints guaranteeing necessary geometrical and topological properties of districts as well as additional objectives and constraints promoting desired seat allocations. For several of the examined municipalities districts solutions with none-suspicious shapes and a more desirable seat allocation for the considered parties given voting outcomes from the 2014 elections were found. The implication of these results for Swedish municipal elections prior to 2015 as well as other elections using similar seat allocation procedures would however be highly dependent on the ability to make detailed and accurate predictions of voting outcomes prior to actual elections.