Contagious McKean-Vlasov systems with heterogeneous impact and exposure

TL;DR

This paper develops a heterogeneous contagious McKean-Vlasov model capturing asymmetric interactions in interbank markets, establishing limit behavior, uniqueness conditions, and jump mechanisms for systemic stability analysis.

Contribution

It introduces a novel heterogeneous formulation of the contagious McKean-Vlasov system with asymmetric interactions and analyzes its limit, uniqueness, and stability properties.

Findings

Characterizes limit points of a finite particle system in interbank contagion.

Establishes global uniqueness under small interaction strength with common noise.

Proposes a method for system jumps to resolve instabilities.

Abstract

We introduce a heterogeneous formulation of a contagious McKean-Vlasov system, whose inherent heterogeneity comes from asymmetric interactions with a natural and highly tractable structure. It is shown that this formulation characterises the limit points of a finite particle system, deriving from a balance sheet based model of solvency contagion in interbank markets, where banks have heterogeneous exposure to and impact on the distress within the system. We also provide a simple result on global uniqueness for the full problem with common noise under a smallness condition on the strength of interactions, and we show that, in the problem without common noise, there is a unique differentiable solution up to an explosion time. Finally, we discuss an intuitive and consistent way of specifying how the system should jump to resolve an instability when the contagious pressures become too large. This is known to happen even in the homogeneous version of the problem, where jumps are specified by a 'physical' notion of solution, but no such notion currently exists for a heterogeneous formulation of the system.