  We investigate how robust the results of committee elections are to small
changes in the input preference orders, depending on the voting rules used. We
find that for typical rules the effect of making a single swap of adjacent
candidates in a single preference order is either that (1) at most one
committee member might be replaced, or (2) it is possible that the whole
committee will be replaced. We also show that the problem of computing the
smallest number of swaps that lead to changing the election outcome is
typically NP-hard, but there are natural FPT algorithms. Finally, for a number
of rules we assess experimentally the average number of random swaps necessary
to change the election result.
