On manipulability of aggregation procedures by coalitions with the same first-ranked alternative
The coalitional manipulability of voting rules for special case of coalition formation is studied by computer experiment. For the considered case, the coalition, upon manipulation, consists of agents with the same alternative on the first place in their orderings. Not necessary all agents of the manipulating coalition should report insincere preferences, i.e. manipulating agents can join others by adjusting the preferences. This makes the coalition formation more flexible, inducing the increase of the Nitzan-Kelly manipulability index by different value for different voting rules. Calculations are made for 3 alternatives for knows aggregation procedures.