The transmission of macroprudential policy in the tails

Álvaro Fernández-Gallardo, Simon Lloyd and Ed Manuel

Since the 2007–09 Global Financial Crisis, central banks have developed a range of macroprudential policies (‘macropru’) to address fault lines in the financial system. A key aim of macropru is to reduce ‘left-tail risks‘ – ie, minimise the probability and severity of future economic crises. However, building this resilience could influence other parts of the GDP-growth distribution and so may not always be costless. In our Working Paper, we gauge these potential costs and benefits by estimating the effects of macropru on the entire GDP-growth distribution, and explore its transmission channels. We find that macropru is effective at reducing the variance of GDP growth, and that it does so by reducing the probability and severity of excessive credit booms.

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Measuring capital at risk in the UK banking sector

Giovanni Covi, James Brookes and Charumathi Raja

How banks are exposed to the financial system and real-economy determines concentration risk and interconnectedness in the banking sector, and in turn, the severity of tail-events. We construct the Global Network data set, a comprehensive exposure-based data set of the UK banking sector, updated quarterly, covering roughly 90% of total assets. We use it to study the UK banking system’s microstructure and estimate the likelihood and severity of tail-events. We find that during the Covid-19 (Covid) pandemic, the likelihood and severity of tail-events in the UK banking sector increased. The probability of an extreme stress event with losses above £91 billion (roughly 19% of CET1 capital) increased from 1% before the pandemic to 4.1% in 2020 Q2, subsequently falling to 1.7% in 2021 Q4.

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Does regulation bite only the less profitable? Evidence from the too big to fail reforms

Tirupam Goel, Ulf Lewrick and Aakriti Mathur

Reforms following the 2008 financial crisis have led to significant increases in banks’ capital requirements. A large literature since then has focused on understanding how banks respond to these changes. Our new paper shows that pre-reform profitability is a vital, but often overlooked, driver of banks’ responses. Profitability determines the opportunity cost of shrinking assets, and underpins the ability to generate capital. We develop a stylised model which predicts that a more profitable bank would choose to shrink by less (or grow by more) compared to a less profitable bank in response to higher capital requirements. Combining textual analysis of banks’ annual reports with the assessment of a key too big to fail (TBTF) reform, we show that this prediction holds in practice.

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On the origin of systemic risk

Giovanni Covi, Mattia Montagna and Gabriele Torri

Systemic risk in the bank sector is often associated with long periods of economic downturn and large social costs. In a new paper, we develop a microstructural contagion model to disentangle and quantify the different sources of systemic risk for the euro-area banking system. Calibrated to granular euro-area data, we estimate that the probability of a systemic banking crisis was around 3.6% in 2018. Seventy per cent of the risk stems from economic risks, with fire sales and contagion risk accounting for most of the remainder and only a small role for interbank exposures. Our findings suggest that correlations among banks’ losses play a crucial role in the origins of systemic risk.

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Playing with fire: banks’ distressed sales under solvency and liquidity constraints

Caterina Lepore and Jamie Coen

Many commentators on the global financial crisis identified ‘fire sales’ as one of the key mechanisms by which shocks to banks were amplified and transmitted across the wider financial system. When firms in distress sell assets held by other institutions at discounted prices, losses can spread through the financial system as prices fall, amplifying the initial stress. In a working paper published last year, we explored this mechanism by presenting a new model of fire sales. In doing so, we answer the following questions: Which types of financial shocks combine to produce fire sales? How can banks optimally liquidate their portfolios when forced to do so? How big a risk are bank fire sales?

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The decline of solvency contagion risk

Marco Bardoscia, Paolo Barucca, Adam Brinley Codd and John Hill

The failure of Lehman Brothers on 15 September 2008 sent shockwaves around the world. But the losses at Lehman Brothers were only the start of the problem. The price of their bonds halved, almost overnight. Other institutions that held Lehman’s debt faced huge losses, and markets feared that those losses could trigger further failures. The good news is that our latest research suggests that risks within the UK banking system from one such contagion channel, “solvency contagion”, have declined sharply since 2008. We have developed a new model which quantifies risk from this channel, and helps us understand why it has fallen. Regulators are using the model to monitor this particular source of risk as part of the Bank’s annual concurrent stress test exercise.

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Bank liquidity requirements: How to get more bang for your buck

Iñaki Aldasoro, Ester Faia, Gerardo Ferrara, Sam Langfield, Zijun Liu and Tomohiro Ota.

We make the case for a macroprudential approach to liquidity requirements in the cross-section of banks. Currently, the liquidity coverage requirement is applied uniformly across banks. This microprudential approach overlooks externalities: owing to their size, complexity and position in the interbank funding network, some banks can cause inordinate damage to the rest of the banking system. When externalities are taken into account, we show that these systemically important banks should be subject to more stringent liquidity requirements. This cross-sectional macroprudential approach promises “more bang for the buck”: systemic risk can be reduced without increasing the stringency of liquidity requirements for the banking system as a whole.

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