Mortgage Risk Weights – revisited

I post on a range of topics in banking but residential mortgage risk weights is one that seems to generate the most attention. I first posted on the topic back in Sep 2018 and have revisited the topic a few times (Dec 2018, June 2019#1, June 2019#2, and Nov 2019) .

The posts have tended to generate a reasonable number of views but limited direct engagement with the arguments I have advanced. Persistence pays off however because the last post did get some specific and very useful feedback on the points I had raised to argue that the difference in capital requirements between IRB and Standardised Banks was not as big as it was claimed to be.

My posts were a response to the discussion of this topic I observed in the financial press which just focussed on the nominal difference in the risk weights (i.e. 25% versus 39%) without any of the qualifications. I identified 5 problems with the simplistic comparison cited in the popular press and by some regulators:

  • Problem 1 – Capital adequacy ratios differ
  • Problem 2 – You have to include capital deductions
  • Problem 3 – The standardised risk weights for residential mortgages seems set to change
  • Problem 4 – The risk of a mortgage depends on the portfolio not the individual loan
  • Problem 5 – You have to include the capital required for Interest Rate Risk in the Banking Book

With the benefit of hindsight and the feedback I have received, I would concede that I have probably paid insufficient attention to the disparity between risk weights (RW) at the higher quality end of the mortgage risk spectrum. IRB banks can be seen to writing a substantial share of their loan book at very low RWs (circa 6%) whereas the best case scenario for standardised banks is a 20% RW. The IRB banks are constrained by the requirement that their average RW should be at least 25% and I thought that this RW Floor was sufficient to just focus on the comparison of average RW. I also thought that the revisions to the standardised approach that introduced the 20% RW might make more of a difference. Now I am not so sure. I need to do a bit more work to resolve the question so for the moment I just want to go on record with this being an issue that needs more thought than I have given it to date.

Regarding the other 4 issues that I identified in my first post, I stand by them for the most part. That does not mean I am right of course but I will briefly recap on my arguments, some of the push back that I have received and areas where we may have to just agree to disagree.

Target capital adequacy ratios differ materially. The big IRB banks are targeting CET1 ratios based on the 10.5% Unquestionably Strong Benchmark and will typically have a bit of a buffer over that threshold. Smaller banks like Bendigo and Suncorp appear to operate with much lower CET1 targets (8.5 to 9.0%). This does not completely offset the nominal RW difference (25 versus 39%) but it is material (circa 20% difference) in my opinion so it seem fair to me that the discussion include this fact. I have to say that not all of my correspondents accepted this argument so it seems that we will have to agree to disagree.

You have to include capital deductions. In particular, the IRB banks are required to hold CET1 capital for the shortfall between their loan loss provision and a regulatory capital value called “Regulatory Expected Loss”. There did not appear to be a great awareness of this requirement and a tendency to dismiss it but my understanding is that it can increase the effective capital requirement by 10-12% which corresponds to an effective IRB RW closer to 28% than 25%.

The risk of a mortgage depends on the overall portfolio not the individual loan. My point here has been that small banks will typically be less diversified than big banks and so that justifies a difference in the capital requirements. I have come to recognise that the difference in portfolio risk may be accentuated to the extent that capital requirements applied to standardised banks impede their ability to capture a fair share of the higher quality end of the residential mortgage book. So I think my core point stands but there is more work to do here to fully understand this aspect of the residential mortgage capital requirements. In particular, I would love get more insight into how APRA thought about this issue when it was calibrating the IRB and standardised capital requirements. If they have spelled out their position somewhere, I have not been able to locate it.

You have to include the capital required for Interest Rate Risk in the Banking Book (IRRBB). I did not attempt to quantify how significant this was but simply argued that it was a requirement that IRB banks faced that standardised banks did not and hence it did reduce the benefit of lower RW. The push back I received was that the IRRBB capital requirement was solely a function of IRB banks “punting” their capital and hence completely unrelated to their residential mortgage loans. I doubt that I will resolve this question here and I do concede that the way in which banks choose to invest their capital has an impact on the size of the IRRBB capital requirement. That said, a bank has to hold capital to underwrite the risk in its residential mortgage book and, all other thinks being equal, an IRB bank has to hold more capital for the IRRBB requirement flowing from the capital that it invests on behalf of the residential mortgage book. So it still seems intuitively reasonable to me to make the connection. Other people clearly disagree so we may have to agree to disagree on this aspect.

Summing up, I had never intended to say that there was no difference in capital requirements. My point was simply that the difference is not as big as is claimed and I was yet to see any analysis that considered all of the issues relevant to properly understand what the net difference in capital requirements is. The issue of how to achieve a more level playing field between IRB and Standardised Banks is of course about much more than differences in capital requirements but it is an important question and one that should be based on a firmer set of facts that a simplistic comparison of the 39% standardised versus 25% IRB RW that is regularly thrown around in the discussion of this question.

I hope I have given a fair representation here of the counter arguments people have raised against my original thesis but apologies in advance if I have not. My understanding of the issues has definitely been improved by the challenges posted on the blog so thanks to everyone who took the time to engage.

Tony

Mortgage risk weights fact check revisited – again

The somewhat arcane topic of mortgage risk weights is back in the news. It gets popular attention to the extent they impact the ability of small banks subject to standardised risk weights to compete with bigger banks which are endorsed to use the more risk sensitive version based on the Internal Ratings Based (IRB) approach. APRA released a Discussion Paper (DP) in February 2018 titled “Revisions to the capital framework for authorised deposit-taking institutions”. There are reports that APRA is close to finalising these revisions and that this will address the competitive disadvantage that small banks suffer under the current regulation.

This sounds like a pretty simple good news story – a victory for borrowers and the smaller banks – and my response to the discussion paper when it was released was that there was a lot to like in what APRA proposed to do. I suspect however that it is a bit more complicated than the story you read in the press.

The difference in capital requirements is overstated

Let’s start with the claimed extent of the competitive disadvantage under current rules. The ACCC’s Final Report on its “Residential Mortgage Price Inquiry” described the challenge with APRA’s current regulatory capital requirements as follows:

“For otherwise identical ADIs, the advantage of a 25% average risk weight (APRA’s minimum for IRB banks) compared to the 39% average risk weight of standardised ADIs is a reduction of approximately 0.14 percentage points in the cost of funding the loan portfolio. This difference translates into an annual funding cost advantage of almost $750 on a residential mortgage of $500 000, or about $15 000 over the 30 year life of a residential mortgage (assuming an average interest rate of 7% over that period).”

You could be forgiven for concluding that this differential (small banks apparently required to hold 56% more capital for the same risk) is outrageous and unfair.

Just comparing risk weights is less than half the story

I am very much in favour of a level playing field and, as stated above, I am mostly in favour of the changes to mortgage risk weights APRA outlined in its discussion paper but I also like fact based debates.

While the risk weights for big banks are certainly lower on average than those required of small banks, the difference in capital requirements is not as large as the comparison of risk weights suggests. To understand why the simple comparison of risk weights is misleading, it will be helpful to start with a quick primer on bank capital requirements.

The topic can be hugely complex but, reduced to its essence, there are three elements that drive the amount of capital a bank holds:

  1. The risk weights applied to its assets
  2. The target capital ratio applied to those risk weighted assets
  3. Any capital deductions required when calculating the capital ratio

I have looked at this question a couple of times (most recently here) and identified a number of problems with the story that the higher risk weights applied to residential mortgages originated by small bank places them at a severe competitive disadvantage:

Target capital ratios – The target capital adequacy ratios applied to their higher standardised risk weighted assets are in some cases lower than the IRB banks and higher in others (i.e. risk weights alone do not determine how much capital a bank is required to hold).

Portfolio risk – The risk of a mortgage depends on the portfolio not the individual loan. The statement that a loan is the same risk irrespective of whether it is written by a big bank or small bank sounds intuitively logical but is not correct. The risk of a loan can only be understood when it is considered as part of the portfolio the bank holds. All other things being equal, small banks will typically be less diversified and hence riskier than a big bank.

Capital deductions – You also have to include capital deductions and the big banks are required to hold capital for a capital deduction linked to the difference between their loan loss provisions and a regulatory capital value called “Regulatory Expected Loss”. The exact amount varies from bank to bank but I believe it increases the effective capital requirement by 10-12% (i.e. an effective RW closer to 28% for the IRB banks).

IRRBB capital requirement – IRB banks must hold capital for Interest Rate Risk in the Banking Book (IRRBB) while the small standardised banks do not face an explicit requirement for this risk. I don’t have sufficient data to assess how significant this is, but intuitively I would expect that the capital that the major banks are required to hold for IRRBB will further narrow the effective difference between the risk weights applied to residential mortgages.

How much does reducing the risk weight differential impact competition in the residential mortgage market?

None of the above is meant to suggest that the small banks operating under the standardised approach don’t have a case for getting a lower risk weight for their higher quality lower risk loans. If the news reports are right then it seems that this is being addressed and that the gap will be narrower. However, it is important to remember that:

  • The capital requirement that the IRB banks are required to maintain is materially higher than a simplistic application of the 25% average risk weight (i.e. the IRB bank advantage is not as large as it is claimed to be).
  • The standardised risk weight does not seem to be the binding constraint so reducing it may not help the small banks much if the market looks through the change in regulatory risk measurement and concludes that nothing has changed in substance.

One way to change the portfolio quality status quo is for small banks to increase their share of low LVR loans with a 20% RW. Residential mortgages do not, for the most part, get originated at LVR of sub 50% but there is an opportunity for small banks to try to refinance seasoned loans where the dynamic LVR has declined. This brings us to the argument that IRB banks are taking the “cream” of the high quality low risk lending opportunities.

The “cream skimming” argument

A report commissioned by COBA argued that:

“While average risk weights for the major banks initially rose following the imposition of average risk weight on IRB banks by APRA, two of the major banks have since dramatically reduced their risk weights on residential mortgages with the lowest risk of default. The average risk weights on such loans is now currently on average less than 6 per cent across the major banks.”

“Despite the imposition of an average risk weight on residential home loans, it appears some of the major banks have decided to engage in cream skimming by targeting home loans with the lowest risk of default. Cream skimming occurs when the competitive pressure focuses on the high-demand customers (the cream) and not on low- demand ones (the skimmed milk) (Laffont & Tirole, 1990, p. 1042). Cream skimming has adverse consequences as it skews the level of risk in house lending away from the major banks and towards other ADIs who have to deal with an adversely selected and far riskier group of home loan applicants.”

“Reconciling Prudential Regulation with Competition” prepared by Pegasus Economics May 2019 (page 43)

It is entirely possible that I am missing something here but, from a pure capital requirement perspective, it is not clear that IRB banks have a material advantage in writing these low risk loans relative to the small bank competition. The overall IRB portfolio must still meet the 25% risk weight floor so any loans with 6% risk weights must be offset by risk weights (and hence riskier loans) that are materially higher than the 25% average requirement. I suspect that the focus on higher quality low risk borrowers by the IRB banks was more a response to the constraints on capacity to lend than something that was driven by the low risk weights themselves.

Under the proposed revised requirements, small banks in fact will probably have the advantage in writing sub 50% LVR loans given that they can do this at a 20% risk weight without the 25% floor on their average risk weights and without the additional capital requirements the IRB banks face.

I recognise there are not many loans originated at this LVR band but there is an opportunity in refinancing seasoned loans where the combined impact of principal reduction and increased property value reduces the LVR. In practice the capacity of small banks to do this profitably will be constrained by their relative expense and funding cost disadvantage. That looks to me to be a bigger issue impacting the ability of small banks to compete but that lies outside the domain of regulatory capital requirements.

Maybe this potential arbitrage does not matter in practice but APRA could quite reasonably impose a similar minimum average RW on Standardised Banks if the level playing field argument works both ways. This should be at least 25% but arguably higher once you factor in the fact that the small banks do not face the other capital requirements that IRB banks do. Even if APRA did not do this, I would expect the market to start looking more closely at the target CET1 for any small bank that accumulated a material share of these lower risk weight loans.

Implications

Nothing in this post is meant to suggest that increasing the risk sensitivity of the standardised risk weights is a bad idea. It seems doubtful however that this change alone will see small banks aggressively under cutting large bank competition. It is possible that small bank shareholders may benefit from improved returns on equity but even that depends on the extent to which the wholesale markets do not simply look through the change and require smaller banks to maintain the status quo capital commitment to residential mortgage lending.

What am I missing …

APRA’s proposed revisions to capital requirements for residential mortgages

… there is a lot to like in what APRA have proposed but also some issues that would benefit from further thought

Many readers will be aware that APRA released a Discussion Paper (DP) last week titled “Revisions to the capital framework for authorised deposit-taking institutions”.   The paper sets out APRA’s proposed changes to ADI capital requirements defined by the Internal Ratings Based Approach (IRB) and Standardised Approach to Credit Risk, Interest Rate Risk in the Banking Book (IRRBB) and Operational Risk. The focus of this post will be the proposals impacting credit risk capital requirements for residential mortgage lending. This post presupposes that the reader is familiar with the detail of what APRA has proposed. For those of you who have not yet got around to reading the whole paper I have added a short summary of the proposals below (see “APRA’s proposals – in more detail”).

My gut reaction is that there is a lot to like in what APRA have proposed but there are also issues that deserve further consideration in order to address the risk of unintended consequence and to better deliver on the objectives of consistency, transparency and competitive neutrality.

Proposals which make sense to me:

  • The increased risk sensitivity of the proposed standardised RWs for residential mortgages is, I believe, a material enhancement of the capital adequacy framework
  • There are arguments (and indeed evidence) for why investor property loans can be as low risk as owner occupier loans (most of the  time) but APRA’s desire to address the systemic tail risk of this form of lending is I think an understandable policy objective for a prudential regulator to pursue
  • Continuing to pursue higher IRB RW via changes to the correlation factor also looks to be a better approach than the 20% floor on LGD currently applied and thankfully also up for revision
  • Applying a higher correlation factor to low PD loans also makes intuitive sense, especially if your primary concern is the systemic risk associated with the residential mortgage lending that dominates the balance sheets of your banking system
  • In addition, the potential for the correlation adjustment to reduce the sensitivity of residential mortgage RWA to the economic cycle (and hence reduce the risk of pro-cyclical stress on capital ratios) is particularly welcome though I believe there is much more to do on this general issue
  • The support for Lender’s Mortgage Insurance (LMI) is also welcome

Areas where I believe the proposed revised capital framework could be improved (or at least benefit from some more thought):

  • The discussion of relative standardised and IRB RW does not address the fact IRB banks are required to hold additional capital to cover any shortfall between loan loss provisions and Regulatory Expected Loss (REL)
  • Residential mortgage portfolios subject to the standardised approach should be subject to a minimum average RW in the same way that IRB portfolios are currently constrained by the 25% floor
  • Applying a fixed scalar to Credit RWA can be problematic as the composition of the loan portfolio continues to evolve

The discussion of comparative IRB and Standardised RW you typically encounter seems to assume that the two approaches are identical in every aspect bar the RW but people working at the coal face know that the nominal RW advantage the IRB banks have has been partly offset by a higher exposure measure the RW are applied to. It appears that APRA’s proposed revisions will partly address this inconsistency by requiring banks using the Standardised Approach to apply a 100% Credit Conversion Factor (CCF) to undrawn loan limits.  IRB banks are also required to take a Common Equity Tier 1 deductions for the shortfall between their loan loss provisions and REL. The proposed revisions do nothing to address this area of inconsistency and in fact the Discussion Paper does not even acknowledge the issue.

Residential mortgage portfolios subject to the standardised approach should be subject to a minimum average RW in the same way that IRB portfolios are constrained. The majority of new residential mortgages are originated at relatively high LVR (most at 70% plus and a significant share at 80% plus), but the average LVR will be much lower as principal is repaid (and even more so if you allow for the appreciation of property values).  The introduction of a 20% RW bucket for standardised banks poses the question whether these banks will have an advantage in targeting the refinancing of seasoned loans with low LVR’s. The IRB banks would seek to retain these customers but they will still be constrained by the 25% average RW mandated by the FSI while the standardised banks face no comparable constraint.

This is unlikely to be an issue in the short term but one of the enduring lessons learned during my time “on the inside” is that banks (not just the big ones) are very good at identifying arbitrages and responding to incentives. It is widely recognised that housing loans have become the largest asset on Australian bank balance sheets (The Royal Commission issued a background paper that cited 42% of assets as at September 2017) but the share was significantly less when I started in banking. There has been a collection of complex drivers at play here (a topic for another post) but the relatively low RW has not harmed the growth of this kind of lending. Consequently, it is dangerous to assume that the status quo will persist if incentives exist to drive a different outcome.

This competitive imbalance could be addressed quite simply if the standardised banks were also subject to a requirement that their average RW was also no lower than 25% (or some alternative floor ratio that adjusted for the differences in exposure and REL noted above).

Another lesson learned “on the inside” is that fixed scalars look simple but are often not. They work fine when the portfolio of assets they are scaling up is stable but will gradually generate a different outcome to what was intended as the composition of the loan book evolves over time. I don’t have an easy solution to this problem but, if you must use them, it helps to recognise the potential for unintended consequence at the start.

Read on below if you have not read the Discussion Paper or want more detail on the revisions APRA has proposed and how these changes are proposed to be reconciled with the FSI recommendation. This is my first real post so feedback would be much appreciated.

Above all, tell me what I am missing … 

Tony

Note: The original version of this post published 22 February 2018 stated that inconsistent measurement of the exposures at default between the standardised and IRB approaches  was not addressed by APRA’s proposed revisions. I believe now that the proposed application of a 100% CCF in the Standardised Approach would in fact address one of the areas of inconsistency. The treatment of Regulatory Expected Loss remains an issue however. The post was revised on 24 February to clarify these points.

APRA’s proposals – in more detail

Good quality loans fully secured by mortgages on occupied residential property (either rented or occupied by the borrower) have been assigned concessionary risk weights (RW) ever since risk weighted capital adequacy ratios were introduced under Basel I (1988). The most concessionary risk weight was initially set at 50% and reduced to 35% in the Basel II Standardised Approach (2006).

APRA currently applies the concessionary 35% RW to standard eligible mortgages with Loan Valuation Ratios (LVR) of 80% or better (or up to 90% LVR if covered by Lender’s Mortgage Insurance) while the best case scenario for a non-standard mortgage is a 50% RW. Progressively higher RW (50/75/100) are applied for higher risk residential mortgages.

Under the Standardised Approach, APRA proposes:

  • The classification of a Standard Eligible Mortgage will distinguish between lowest risk “Owner-occupied P&I” and a higher risk “Other residential mortgages” category which is intended to be conceptually similar to the “material dependence” concept employed by Basel III to distinguish loans where repayment depends materially on the cash flows generated by the property securing the loan
  • 6 RW bands for each of these two types of residential mortgage (compared to 5 bands currently)
  • Standard Eligible Mortgages with lower LVR loans to be assigned lower RW but these loans must also meet defined serviceability, marketability and valuation criteria to qualify for the concessionary RW
  • The higher RW applied to “Other residential mortgages” may take the form of a fixed risk-weight schedule (per the indicative RW in Table 3 of the Discussion Paper) but might also be implemented via a multiplier, applied to the RW for owner-occupied P&I loans, which might vary over time “… depending on prevailing prudential or financial stability objectives or concerns”
  • Relatively lower capital requirements to continue to apply where loans are covered by LMI but its preferred approach is to apply a RW loading to loans with LVR in excess of 80% that are not insured (i.e. the indicative RW in Table 3 assume that LMI covers the high LVR loans)
  • Non-Standard residential mortgages should no longer benefit from any RW concession and be assigned a flat 100% RW irrespective of LVR and LMI

While the IRB requirements impacting residential mortgages are largely unchanged under Basel III, APRA proposes the following changes to the Australian IRB Approach to reflect local requirements and conditions:

  • Increased capital requirements for investment and interest-only exposures; to be implemented via a higher correlation factor for these loans
  • The (currently fixed) correlation factor applied to residential mortgages to be amended to depend on probability of default (PD); reflecting empirical evidence that “… the default risk of lower PD exposures is more dependent on the economic cycle  and can consequently increase at a relatively higher rate in a downturn”
  • A reduction in the minimum Loss Given Default (LGD) from 20% to 10% (subject to APRA approval of the LGD model); in order to facilitate “… better alignment of LGD estimates to key drivers of loss such as LVR and LMI”
  • Capital requirements for non-standard mortgages use the standardised approach; increasing consistency between the IRB an standardised approaches

APRA’s proposals seek to strike a balance between risk sensitivity and simplicity but must also take account of the FSI recommendations that ADI capital levels be unquestionably strong while also narrowing the difference between standardised and IRB RWs for residential mortgages. APRA is undertaking a Quantitative Impact Study (QIS) to better understand the impact of its proposals but the DP flagged that APRA does not expect the changes to correlation factors to meet its objectives for increased capital for residential mortgage exposures.

APRA could just further ramp up the correlation factor to generate the target IRB RW (which I assume continues to be 25%) but the DP notes that this would create undesirable inconsistencies with the correlation factors applied to other asset classes. Consequently, the DP indicates that the target increase in IRB RWA will likely be pursued via

  • A fixed multiplier (scalar) applied to total Credit RWA (i.e. althoughBasel III removes the 1.06 Credit RWA scalar, APRA is considering retaining a scalar with a value yet to be determined); and
  • If necessary, by applying additional specific RWA scalars for residential (and commercial) property.

These scalars will be subject to consultation with the industry and APRA has committed to review the 10.5% CET1 benchmark for unquestionably strong capital should the net result of the proposed revisions result in an overall increase in RWA’s relative to current methodologies.