Sovereign bonds are widely used as collateral in banks’ funding and trading operations. If a sovereign becomes distressed, the collateral mechanism impairs and banks are suddenly facing significant liquidity calls. Basel III's Liquidity Coverage Ratio (LCR) protects banks against unexpected liquidity calls, but currently excludes sovereign distress. Thus, all banks fulfilling the LCR are still exposed to a liquidity risk stemming from distressed sovereign debt and materializing through the collateral channel. Our paper shows that this unaddressed risk can translate into a system-wide liquidity shock. To gauge the potential damage caused by such a shock, we develop a model based on banks’ home sovereign exposures and a bundle of simplifying assumptions in which sovereign distress triggers bank distress. Our model describes how deteriorating sovereign collateral can lead to an overall liquidity squeeze and non-compliance with Basel III liquidity standards. As this risk is too material to be neglected, we propose an alternative version of the LCR, LCR+, which includes the liquidity impact of sovereign distress.

We propose measuring a bank’s distance to compliance with Basel III using a portfolio that makes the bank compliant. This “Distance to Compliance” portfolio describes an implementable strategy and incorporates the interactions of all Basel III ratios. We derive the portfolio in a microeconomic banking model in which the board decides on the regulatory target levels and bears the responsibility in case the bank fails to meet the regulatory requirements in a stress situation. We apply our framework to two hypothetical banks and find that they achieve compliance by growth strategies without cutting lending. We corroborate that shareholders choose different compliance strategies than managers, emphasizing the importance of setting managers’ incentives carefully. We compare our results to findings from impact studies that are not model-based and do not consider the interactions of the Basel III ratios. We observe that the synergies of LCR and NSFR are the most pronounced ones but of secondary order in absolute magnitude. This means that measuring “Distance to Compliance” on a ratio-by-ratio basis omitting synergies, as often done by regulators, does not introduce a major bias.

Large banking groups face the question of how to optimally allocate and generate liquidity: in a central liquidity hub or in many decentralized branches. We translate this question into a facility location problem under uncertainty. We show that volatility is the key driver behind (de-)centralization. We provide an analytical solution for the 2-branch model and show that a liquidity center can be interpreted as an option on immediate liquidity. Therefore, its value can be interpreted as the price of information, i.e., the price of knowing the exact demand. Furthermore, we derive the threshold above which it is advantageous to open a liquidity center and show that it is a function of the volatility and the characteristic of the bank network. Finally, we discuss the n-branch model for real-world banking groups (10–60 branches) and show that it can be solved with high granularity (100 scenarios) within less than 30s.

In addition to the Basel II capital ratio, Basel III requires banks to respect additional ratios, such as leverage ratio, liquidity coverage ratio and net stable funding ratio. Banks are required to be compliant with all four constraints simultaneously. Our article provides a framework for banks to help their search for an optimal transition from Basel II to Basel III. Recognizing that banks’ return and the four constraints are of linear type, this search can be formulated as a linear program and solved by standard software. Incorporating uncertainty on future defaults, risk weights and withdrawals and formulating the problem as a Chance constrained model does not only yield optimal transition strategies but also determines the internal thresholds for the Basel III-ratios. Our approach needs two standard inputs from controlling: profit margins per product and non-financial adjustment costs to expand or cut back business. The adjustment cost can be used to calibrate the model to the current business mix. This calibration can be done by bank outsiders and allows the model to be used in impact studies to replace ad hoc strategies. To highlight its practicality, we apply our model to a typical German bank with a business mix that complies with Basel II, but not with the Basel III-, capital-, leverage- and net stable funding-ratio. Assuming that its business model is optimal under Basel II, we find that this bank would achieve compliance restructuring its funding side by replacing interbank funding by capital and retail deposits. Additional uncertainty would amplify the magnitude of the changes, but would still affect the same positions. These findings are robust against alternative margin definitions and adjustment cost levels.