# Llull and Copeland Voting Computationally Resist Bribery and Control

@article{Faliszewski2008LlullAC, title={Llull and Copeland Voting Computationally Resist Bribery and Control}, author={Piotr Faliszewski and Edith Hemaspaandra and Lane A. Hemaspaandra and J{\"o}rg Rothe}, journal={ArXiv}, year={2008}, volume={abs/0809.4484} }

The only systems previously known to be resistant to all the standard control types were highly artificial election systems created by hybridization. We study a parameterized version of Copeland voting, denoted by Copeland^\alpha, where the parameter \alpha is a rational number between 0 and 1 that specifies how ties are valued in the pairwise comparisons of candidates. We prove that Copeland^{0.5}, the system commonly referred to as "Copeland voting," provides full resistance to constructive…

## 27 Citations

Copeland Voting Fully Resists Constructive Control

- MathematicsAAIM
- 2008

It is proved that Copeland0.5, the system commonly referred to as "Copeland voting," provides full resistance to constructive control, among systems with a polynomial-time winner problem, this is the first natural election system proven to have full resistanceto constructive control.

Llull and Copeland Voting Computationally Resist Bribery and Constructive Control

- MathematicsJ. Artif. Intell. Res.
- 2009

Among systems with a polynomial-time winner problem, Copeland voting is the first natural election system proven to have full resistance to constructive control and vulnerability results for microbribery are proven via a novel technique involving min-cost network flow.

Challenges to complexity shields that are supposed to protect elections against manipulation and control: a survey

- Computer ScienceAnnals of Mathematics and Artificial Intelligence
- 2013

This work surveys and discusses some recent results on challenges to complexity results for manipulation and control, including typical-case analyses and experiments, fixed-parameter tractability, domain restrictions, and approximability.

Computational Aspects of Approval Voting 1

- Computer Science
- 2009

Since re-strategy preferencebased approval voting (SP-AV), a variant of approval voting propo sed by Brams and Sanver [BS06], is computationally resistant to 19 of the 22 common types of control, SP-AV is the system known to display the broadest resistance to control.

Iterative voting and multi-mode control in preference aggregation

- EconomicsIntelligenza Artificiale
- 2014

This work analyzes two different scenarios, which can be seen as two different sides of the same problem, and usesingle and multiple control actions within iterative voting, in order to understand if the malicious side of control can overcome the stability of the Iterative voting systems.

Normalized Range Voting Broadly Resists Control

- EconomicsTheory of Computing Systems
- 2012

It is shown that Range Voting and Normalized Range Voting has among the largest known number of control resistances among natural voting systems.

Sincere‐Strategy Preference‐Based Approval Voting Fully Resists Constructive Control and Broadly Resists Destructive Control

- EconomicsMath. Log. Q.
- 2009

SP-AV is the second natural voting system with an easy winner-determination procedure that is known to have full resistance to constructive control, and unlike Copeland voting it in addition displays broad resistance to destructive control.

Parameterized complexity of candidate control in elections and related digraph problems

- Computer ScienceTheor. Comput. Sci.
- 2008

Binary linear programming solutions and non-approximability for control problems in voting systems

- Computer ScienceDiscret. Appl. Math.
- 2014

Controlling Elections by Replacing Candidates: Theoretical and Experimental Results

- Computer ScienceMPREF@AAAI
- 2014

This study shows that the theoretical computational complexity results are often not reflecting the practical difficulty of controlling elections by replacing candidates, so Plurality and Veto are focused in particular on.

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