Majority decisions when abstention is possible

Suppose that we are given a family of choice functions on pairs from a given finite set. The set is considered as a set of alternatives (say candidates for an office) and the functions as potential “voters.” The question is, what choice functions agree, on every pair, with the majority of some finite subfamily of the voters? For the problem as stated, a complete characterization was given in Shelah (2009) 7], but here we allow voters to abstain. Aside from the trivial case, the possible families of (partial) choice functions break into three cases in terms of the functions that can be generated by majority decision. In one of these, cycles along the lines of Condorcet’s paradox are avoided. In another, all partial choice functions can be represented.