Fair Division and Redistricting

Abstract: Recently, Landau, Reid and Yershov provided a novel solution to the problem of redistricting. Instead of trying to ensure fairness by restricting the shape of the possible maps or by assigning the power to draw the map to nonbiased entities, the solution ensures fairness by balancing competing interests against each other. This kind of solution is an example of what are known as "fair division" solutions--- such solutions involve the preferences of all parties and are accompanied by rigorous guarantees of a specified well-defined notion of fairness. In this expository article, we give an introduction to the ideas of fair division in the context of this redistricting solution. Through examples and discussion we clarify how fair division methods can play an important role in a realistic redistricting solution by introducing an interactive step that incorporates a certain kind of fairness that can be used in concert with, and not a substitute for, other necessary or desired criteria for a good redistricting solution.