An impossibility theorem concerning positive involvement in voting
证明了一个新的不可能性定理：不存在同时满足正向参与公理、孔多塞胜者与败者准则、可分辨性以及一种常见不变性性质的序数投票方法。
In social choice theory with ordinal preferences, a voting method satisfies the axiom of positive involvement if adding to a preference profile a voter who ranks an alternative uniquely first cannot cause that alternative to go from winning to losing. In this note, we prove a new impossibility theorem concerning this axiom: there is no ordinal voting method satisfying positive involvement that also satisfies the Condorcet winner and loser criteria, resolvability, and a common invariance property for Condorcet methods, namely that the choice of winners depends only on the ordering of majority margins by size.