Evaluation of the Degree of Manipulability of Positional Aggregation Procedures in a Dynamic Voting Model

The degree of individual manipulability of positional aggregation procedures is evaluated for the dynamic voting model within the framework of the two-dimensional Downsian model. In the dynamic voting model, alternatives move in steps toward a central point while agents attempt to manipulate at each step. The share of manipulable profiles, i.e., the Nitzan-Kelly index, is calculated. The manipulability of Plurality, Approval, Inverse Plurality, Borda, Threshold, Nanson, Inverse Borda, Hare, and Coombs aggregation procedures is evaluated at each step of the movement. Computer simulation shows that the Hare, Coombs, and Threshold procedures are among the least manipulable ones.