Proportional Clustering, the ${\hat{I}}^2$-Plurality Problem, and Metric Distortion

Abstract

We show that the proportional clustering problem using the Droop quota for $k=1$ is equivalent to the ${\hat{I}}^2$-plurality problem. We also show that the Plurality Veto rule can be used to select ($\sqrt{5}-2$)-plurality points using only ordinal information about the metric space and resolve an open question of Kalayci et al. (AAAI 2024) by proving that $(2+\sqrt{5})$-proportionally fair clusterings can be found using purely ordinal information.