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Big City vs. the Great Outdoors Voter Distribution and How It Affects Gerrymandering
Allan Borodin, Omer Lev, Nisarg Shah, Tyrone Strangway
Big City vs. the Great Outdoors Voter Distribution and How It - - PowerPoint PPT Presentation
Big City vs. the Great Outdoors Voter Distribution and How It - - PowerPoint PPT Presentation
Big City vs. the Great Outdoors Voter Distribution and How It Affects Gerrymandering Allan Borodin, Omer Lev, Nisarg Shah, Tyrone Strangway Gerrymandering Gerrymandering Gerrymandering Gerrymandering proportional Gerrymandering Red
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Gerrymandering
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Gerrymandering
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Gerrymandering proportional
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Gerrymandering Red
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Gerrymandering blue
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Gerrymandering complexity
Open question:
Is dividing a planar graph into 2 equal sized connected components NP-hard?
(Dyer and Frieze 1985 show NP-hard for general graphs, and hypothesize same in planar case)
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Goals
Prevent gerrymandering!!
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Goals
Prevent gerrymandering!!
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Goals
Prevent gerrymandering!! Detect gerrymandering!!
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Goals
Prevent gerrymandering!! Detect gerrymandering!!
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Goals
Prevent gerrymandering!! Detect gerrymandering!! Study the effect of voter distribution on gerrymandering
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Gerrymandering power
The difference between the number of districts a party should have, under a fairness criterion (e.g., proportional to its support size) and the maximal number of districts it can get under optimal gerrymandering.
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Homogenous population
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Recently… US (2016)
48.04% 45.95%
Popular vote:
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US 2016 results, geography
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US 2016 results, geography & population
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Recently… UK (2010)
36.1% 29%
Popular vote:
47.08% 39.69%
MP share:
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UK 2010 results, geography
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UK 2010 results, geography & population
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Continuous grid
Vote share → Seat share → Best case Worst case
For voter densities "1 and "2: For worst case: a sharp transition at 50%
(in best case, can’t achieve more than double their voter share)
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Discrete grid
For 2 districts
! " + ! $ voting share guarantees winning both
districts
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Urban / rural divide
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Urban / rural divide
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Urban / rural divide
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Optimal Gerrymandering
Vote Share 55:45 Urban
- ptimal
share ~44:56 Rural
- ptimal
share ~66:34
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Urban / rural divide urban=40%;rural=60%
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Urban / rural divide
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What’s next?
Data, data, DATA! More robust simulations Suburb/exurb effect? More variables, more explanation power Axiomatic approach? Extend theory: larger grids different voter distributions
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