Lot-based voting rules

The Internet Engineering Task Force develops and promotes Internet standards like TCP/IP. The chair of the Task Force is chosen by an election which starts with a set of voters being selected at random from the electorate of volunteers. Selecting decision makers by lottery like this has a long and venerable history, having been used in Athenian democracy over two millennia ago, as well as for over 500 years from the 13th Century to elect the Doge of Venice. In this paper, we consider using such lotteries in multi-agent decision making. We study a family of voting rules called lot-based voting rules. Such rules have two steps: in the first step, k votes are selected by a lottery, then in the second round (the runoff), a voting rule is applied to select the winner based on these k votes. We study some normative properties of such lot-based rules. We also investigate the computational complexity of computing the winner with weighted and unweighted votes, and of computing manipulations. We show that for most lot-based voting rules winner determination and manipulation are computationally hard. Our results suggest that this general technique (using lotteries to selecting some voters randomly) may help to prevent strategic behavior of the voters from a computational point of view.