Sandcastles and Financial Systems: A Sandpile Metaphor

Social welfare costs from bank resolution, including contagion and moral hazard, are often thought to be minimized when supervisors can direct the merger of a failing bank with a sound, healthy one. However, social losses may become even larger if the absorbing institutions fail themselves. We ask whether social welfare losses are indeed lower when supervisors intervene rather than not. We use the sand pile/Abelian model as a metaphor to model financial losses which, as sand grains that fall onto a pile, eventually lead to a slide/failure. When capital in the system is insufficient to absorb the failing institution there will be welfare losses. Results suggest that, over the longer-term, social costs are lower when supervisors manage mergers. Additionally, financial networks that have a structure that minimizes social losses also minimize crises frequency. However, the bank employed resolution strategy will determine which financial network structures are associated with the minimum average loss per bankruptcy event.