RBNZ COVID 19 Stress Tests

The RBNZ just released the results of the stress testing conducted by itself and a selection of the larger NZ banks to test resilience to the risks posed by COVID 19.

The extract below summarises the process the RBNZ followed and its key conclusions:

 COVID-19 stress test consisted of two parts. First, a desktop stress test where the Reserve Bank estimated the impact on profitability and capital for nine of New Zealand’s largest banks to the impact of two severe but plausible scenarios. Second, the Reserve Bank coordinated a process in which the five largest banks used their own models to estimate the effect on their banks for the same scenarios.

  The pessimistic baseline scenario can be characterised as a one-in-50 to one-in-75 year event with the unemployment rate rising to 13.4 percent and a 37 percent fall in property prices. In the very severe scenario, the unemployment rate reaches 17.7 percent and house prices fall 50 percent. It should be noted that these scenarios are hypothetical and are significantly more severe than the Reserve Banks’ baseline scenario.

  The overall conclusion from the Reserve Bank’s modelling is that banks could draw on their existing capital buffers and continue lending to support lending in the economy during a downturn of the severity of the pessimistic baseline scenario. However, in the more severe scenario, banks capital fell below the regulatory minimums and would require significant mitigating actions including capital injections to continue lending. This reinforces the need for strong capital buffers to provide resilience against severe but unlikely events.

  The results of this stress test supports decisions that were made as part of the Capital Review to increase bank capital levels. The findings will help to inform Reserve Bank decisions on the timing of the implementation of the Capital Review, and any changes to current dividend restrictions.

“Outcome from a COVID-19 stress test of New Zealand banks”, RBNZ Bulletin Vol 83, No 3 September 2020

I have only skimmed the paper thus far but there is one detail I think worth highlighting for anyone not familiar with the detail of how bank capital adequacy is measured – specifically the impact of Risk Weighted Assets on the decline in capital ratios.

The RBNZ includes two useful charts which decompose the aggregate changes in CET1 capital ratio by year two of the scenario.

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In the “Pessimistic Baseline Scenario”(PBS), the aggregate CET1 ratio declines 3.7 percentage points to 7.7 percent. This is above both the regulatory minimum and the threshold for mandatory conversion of Additional Tier 1 Capital. What I found interesting was that RWA growth contributed 2.2 percentage points to the net decline.

The RBNZ quite reasonably points out that banks will amplify the downturn if they restrict the supply of credit to the economy but I think it is also reasonable to assume that the overall level of loan outstandings is not growing and may well be shrinking due to the decline in economic activity. So a substantial portion of the decline in the aggregate CET1 ratio is due to the increase in average risk weights as credit quality declines. The C ET1 ratio is being impacted not only by the increase in impairment expenses reducing the numerator, there is a substantial added decline due to the way that risk weighted assets are measured

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In the “Very Severe Scenario”(VSS), the aggregate CET1 ratio declines 5.6 percentage points to 5.8 percent. The first point to note here is that CET1 only remains above the 4.5% prudential minimum by virtue of the conversion of 1.6 percentage points of Additional Tier 1 Capital. Assuming 100% of AT1 was converted, this also implies that the Tier 1 ratio is below the 6.0% prudential minimum.

These outcomes provide food for thought but I few points I think wroth considering further before accepting the headline results at face value:

• The headline results are materially impacted by the pro cyclicality of the advanced forms of Risk Weighted Asset measurement – risk sensitive measures offer useful insights but we also need to understand they ways in which they can also amplify the impacts of adverse scenarios rather than just taking the numbers at face value
• The headline numbers are all RBNZ Desktop results – it would be useful to get a sense of exactly how much the internal stress test modelling conducted by the banks varied from the RBNZ Desktop results – The RBNZ stated (page 12) that the bank results were similar to its for the PBS but less severe in the VSS.

As always, it is entirely possible that I am missing something but I feel that the answer to bank resilience is not just a higher capital ratio. A deeper understanding of the pro cyclicality embedded in the system will I think allow us to build a better capital adequacy framework. As yet I don’t see this topic getting the attention it deserves.

Tony – From the Outside