Low Risk Residential Mortgage Risk Weights

I have posted a number of times on the question of residential mortgage risk weights, either on the general topic of the comparison of the risk weights applied to the standardised and IRB ADIs (see here) or the reasons why risk weights for IRB ADIs can be so low (see here).

On the question of relative risk weights, I have argued that the real difference between the standardised and IRB risk weights is overstated when framed in terms of simplistic comparisons of nominal risk weights that you typically read in the news media discussion of this question. I stand by that general assessment but have conceded that I have paid insufficient attention to the disparity in risk weights at the higher quality end of the mortgage risk spectrum.

A Discussion Paper released by APRA offers a useful discussion of this low risk weight question as part of a broader set of proposals intended to improve the transparency, flexibility and resilience of the Australian capital adequacy framework.

In section 4.2.1 of the paper, APRA notes the concern raised by standardised ADIs…

A specific concern raised by standardised ADIs in prior rounds of consultation has been the difference in capital requirements for lending at low LVRs. Stakeholders have noted that the lowest risk weight under the standardised approach would be 20 per cent under the proposed framework, but this appears to be significantly lower for the IRB approach. In response to this feedback, APRA has undertaken further analysis at a more detailed level, noting the difference in capital requirements that need to be taken into account when comparing capital outcomes under the standardised and IRB approaches (see Box 2 above).

But APRA’s assessment is that the difference is not material when you look beyond the simplistic comparison of risk weights and consider the overall difference in capital requirements

APRA does not consider that there is a material capital difference between the standardised and IRB approaches at the lower LVR level. For loans with an LVR less than 60 per cent, APRA has estimated that the pricing differential that could be reasonably attributed to differences in the capital requirements between the two approaches would be lower than the differential at the average portfolio outcome.

In explaining the reasons for this conclusion, APRA addresses some misconceptions about the IRB approach to low LVR lending compared to the standardised approach

In understanding the reasons for this outcome, it is important to understand the differences in how the standardised and IRB approaches operate. In particular, there are misconceptions around the capital requirement that would apply to low LVR lending under the IRB approach. For example, it would not be appropriate to solely equate the lowest risk weight reported by IRB ADIs in market disclosures with low LVR loans. The IRB approach considers a more complex range of variable interactions compared to the standardised approach. Under the standardised approach, a low risk weight is assigned to a loan with a low LVR at origination.

One of the key points APRA makes is that IRB ADIs do not get to originate loans at the ultra low risk weights that have been the focus of much of the concern raised by standardised ADIs.

In particular, IRB estimates are more dynamic through the life of the loan, for example, they are more responsive to a change in borrower circumstances or movements in the credit cycle. Standardised risk weights generally do not change over the life of a loan. For an IRB ADI, the lowest risk weight is generally applied to loans that have significantly prepaid ahead of schedule. A low LVR loan on the standardised approach is not necessarily assigned the lowest risk weight under the IRB approach at origination.

APRA states that it is not appropriate to introduce “dynamic”factors into the standardised risk weight framework.

APRA is not proposing to include dynamic factors in determining risk weights under the standardised approach for the following reasons:

– the standardised approach is intended to be simple and aligned with Basel III. For the standardised approach, APRA considers it more appropriate to focus on origination rather than behavioural variables as this has more influence on the quality of the portfolio and leads to less procyclical capital requirements; and

– the average difference between standardised and IRB capital outcomes is much narrower at the point of origination, which is the key point for competition. While the difference between standardised and IRB capital outcomes could widen over the life of the loan, APRA has ensured that the difference in average portfolio outcomes remains appropriate

But that it does intend to introduce a 5 per cent risk weight floor into the IRB approach to act as a backstop.

That said, APRA is proposing to implement a 5 per cent risk-weight floor for residential mortgage exposures under the IRB approach, to act as a simple backstop in ensuring capital outcomes do not widen at the lower risk segment of the portfolio. This is consistent with the approach taken by other jurisdictions and will limit the difference in capital outcomes between the standardised and IRB approaches for lower risk exposures. This risk-weight floor is in addition to other factors that will reduce the difference in capital outcomes between standardised and IRB ADIs, such as the higher CCB for IRB ADIs and lower CCF estimates for standardised ADIs.

As always, it remains possible that I am missing something. The explanation offered by APRA however gives me confidence that my broad argument about the overstatement of the difference has been broadly correct. Equally importantly, the changes to residential mortgage risk weights proposed in the Discussion Paper will further reduce the gap that does exist.

Tony – From the Outside