Central Counterparty Resilience in Financial Networks: An Analysis of Default Waterfall Mechanics

Abstract

Central counterparties (CCPs) have become systemically important institutions in modern financial markets following the regulatory reforms introduced after the 2007–2009 financial crisis. By inserting themselves as the new buyer to every seller and new seller to every buyer in a derivatives transaction, CCPs eliminate counterparty credit risk between clearing members. When a clearing member cannot meet its obligations, losses are absorbed through the so called default waterfall, an ordered sequence of prefunded financial resources drawn upon layer by layer before losses can propagate to the broader financial system. Despite their importance, existing research tends to examine the de sign of these resources and the structure of the financial network in which a CCP operates in isolation, leaving open whether resilience benefits are robust across struc turally different clearing environments. This thesis addresses that gap by integrating the financial network clearing model of Eisenberg and Noe (2001) with the CCP default waterfall framework of Ghamami et al. (2022) across three synthetic network topologies of increasing structural complexity. The framework allows for the controlled variation of two key design dimensions simultaneously, namely the severity of an exogenous mar ket shock, and the allocation between initial margin (IM), member-specific collateral posted to cover individual position risk, and the default fund (DF), the shared pool through which losses exceeding IM are mutualised across surviving clearing members. Our numerical studies render three main findings. First, heterogeneous, hub-driven networks exhibit lower shock thresholds for CCP default and sharper loss escalation than dispersed structures. Second, the Cover-2 calibration standard is more sensi tive to hub concentration than a uniform regulatory framework. This implies holding network size and connectivity constant, greater exposure concentration among hub members raises the required default fund. Consequently, identical regulatory rules produce meaningfully different levels of effective protection across markets. Third, re allocating IM toward the DF reduces CCP default probability more effectively than increasing total collateral by an equivalent amount, with the benefit materialising at lower shock thresholds in concentrated networks. This gain, however, comes at a direct cost to surviving members, whose resources are drawn upon to cover defaulting mem bers’ shortfalls, creating rational incentives to resist the system-optimal level of loss mutualisation. Collectively, these results suggest that regulatory frameworks cannot rely on a uniform approach. Accounting for both network topology and the incentive tensions inherent in loss mutualisation is imperative for effective CCP oversight.