Borda aggregation dynamics of preference orderings on networks

Abstract

We introduce and analyze a discrete-time network process in which each node holds a (weak) preference ordering over a finite set of alternatives and updates by local Borda aggregation . At each step, a node forms a weighted average (row-stochastic random-walk normalization) of its neighbors’ Borda score vectors and projects the aggregated score back to a weak order. Updates are bounded : in each round, a node advances by at most one step along a shortest path in the preference graph toward its local Borda target, reflecting incremental preference revision. Our emphasis is dynamical: we develop sufficient conditions, stated directly in terms of graph topology and weights, for (i) self-sustained oscillations in the absence of persistent sources, and (ii) forced oscillations under contrarian persistent camps. We show that these oscillatory phenomena are robust features of the Borda-aggregation coupling, driven by the topology of the influence network and the geometry of the preference space rather than by the bounded-step rule per se. We also record robustness (structural stability) away from score-tie hyperplanes and contrast synchronous (Variant S) and asynchronous (Variant A) updating.