HOW BANKING WORKS · CAPITAL 43
If every risk model says the balance sheet is safe, banking still needs one question that does not depend heavily on those risk weights
Risk-weighted capital ratios are useful because they distinguish safer exposures from riskier ones. But that usefulness creates a weakness: the denominator depends on rules, classifications, models and assumptions about risk.
The bank leverage ratio is designed as a backstop. It compares Tier 1 capital with a broad exposure measure that is much less dependent on risk weights.
Its job is not to replace risk-sensitive capital requirements. Its job is to stop a bank from becoming extremely leveraged merely because measured risk appears unusually low.
This article continues Batch 11 under How Banking Works.
The basic leverage-ratio idea
leverage ratio = Tier 1 capital ÷ leverage exposure measure.
The exact regulatory calculation is technical. The exposure measure is broader than simple accounting assets and can include on-balance-sheet exposures, derivatives, securities-financing transactions and certain off-balance-sheet commitments under the applicable Basel rules.
The official technical source is the Basel Framework.
Why risk-weighted capital ratios need a backstop
Suppose a bank holds a very large portfolio of assets that receive low risk weights. Its risk-weighted assets can remain modest relative to total exposure. The bank can therefore look strongly capitalised on an RWA basis even while the absolute size of the balance sheet becomes enormous.
If the risk weights prove too optimistic, a small percentage loss applied to a very large asset base can still overwhelm capital.
small measured risk × very large exposure can still create a very large loss.
The leverage ratio limits how far that logic can run.
Leverage means using liabilities to support a larger asset base than equity alone could fund
Imagine a bank with S$5 billion of equity supporting S$100 billion of assets. Most of the balance sheet is funded by deposits and other liabilities.
If assets fall in value by 1 per cent—S$1 billion—equity falls by 20 per cent. If assets fall by 5 per cent, the simple accounting equity layer can be exhausted.
Leverage magnifies the effect of asset-value changes on the residual capital layer.
A simple leverage example
| Bank | Capital | Broad exposure | Simple leverage intuition |
|---|---|---|---|
| Bank A | S$10bn | S$100bn | More capital per unit of exposure |
| Bank B | S$10bn | S$250bn | Less capital per unit of exposure |
Even if Bank B’s assets receive lower average risk weights, its capital has to protect a much larger absolute exposure base.
The leverage ratio is deliberately less risk-sensitive
This is both its weakness and its strength.
It does not distinguish finely between every safe and risky exposure, so it can make very low-risk assets appear capital-intensive relative to an RWA-based measure. But because it is less sensitive to risk modelling, it is harder to improve the ratio merely by assigning lower measured risk to the same underlying balance sheet.
The leverage ratio therefore acts as a floor under model optimism.
Why the denominator is not simply “total assets”
Some banking exposures do not appear as ordinary balance-sheet assets in a way that captures their full leverage effect. Derivatives can create future exposure. Securities-financing transactions can create financing chains. Undrawn commitments can become funded later.
The regulatory leverage exposure measure therefore applies specific treatment to these categories rather than relying only on the accounting asset total.
The public lesson is simple: leverage can hide outside the line labelled “total assets.”
Derivatives can create large gross exposures with small current values
A derivative can have a small net fair value today while representing a much larger contractual notional amount and future exposure. Netting and collateral reduce risk, but the bank still needs a prudent exposure measure.
This is one reason leverage rules include specific derivative calculations instead of simply adding today’s accounting value.
Securities-financing transactions can increase balance-sheet leverage
Repo and similar transactions can raise cash against securities and support additional positions. They are useful for liquidity and market functioning, but repeated secured financing can expand gross exposures and interconnectedness.
The leverage ratio therefore looks beyond whether the transaction is secured. Collateral reduces credit loss; it does not make leverage disappear.
Read Secured Bank Funding for the funding side.
Off-balance-sheet commitments matter because customers can draw them
A bank can promise a customer S$100 million of credit while only S$20 million is currently drawn. The remaining S$80 million can still become funded exposure later.
Leverage rules apply conversion factors to relevant off-balance-sheet items so the bank cannot make very large commitments and treat them as if they carried no balance-sheet consequence.
Why the leverage ratio becomes binding for some business models
A bank holding many low-risk-weight assets can have a strong RWA-based capital ratio while its leverage ratio becomes the tighter constraint. That means the bank cannot expand the balance sheet further without adding more Tier 1 capital or reducing exposure.
This is intentional. The backstop becomes most useful when the risk-weighted denominator is unusually small relative to total exposure.
A leverage constraint can affect low-risk businesses
Because the leverage ratio is intentionally less risk-sensitive, it can make some very low-risk, high-volume activities consume meaningful capital. This can affect market-making, secured financing or sovereign-heavy portfolios depending on the institution and jurisdiction.
That trade-off is part of the design. A backstop that perfectly reproduced risk weights would no longer be an independent backstop.
Risk-weighted ratios and leverage ratios answer different questions
| Measure | Main question |
|---|---|
| Risk-weighted capital ratio | Does capital look sufficient for the measured risk of the bank’s exposures? |
| Leverage ratio | Does the bank have enough Tier 1 capital relative to a broad exposure measure even if measured risk is low? |
The two views overlap. Their disagreement is often informative.
Read Risk-Weighted Assets for the risk-sensitive denominator.
Model risk is exactly why the backstop exists
Every risk model simplifies reality. Historical data may omit future crises. Correlations can rise. Collateral values can fall together. Internal ratings can drift. A low measured probability of default can be wrong.
If all capital requirements depended on those same models, one systematic modelling error could reduce capital across the system.
The leverage ratio deliberately asks a cruder but harder question: how much broad exposure is this capital actually supporting?
Leverage can build quietly in good times
When asset prices are stable and defaults are low, measured risk can fall. Banks can respond by expanding balance sheets. The expansion can reinforce asset demand and compress risk measures further.
A non-risk-based backstop limits that procyclical loop by requiring capital against exposure even when measured risk looks benign.
A leverage ratio cannot tell whether the bank is liquid
A bank can have a strong leverage ratio and still face deposit outflows it cannot meet. The ratio does not replace HQLA, liquidity coverage, stable funding or contingency planning.
Capital and liquidity remain separate survival systems.
Read Liquidity Coverage and Stable Funding.
A leverage ratio cannot tell whether exposures are concentrated
Two banks can have the same leverage ratio. One can hold diversified assets while the other is concentrated in a single sector or counterparty.
The leverage ratio sees quantity better than risk composition. That is why it complements rather than replaces risk-weighted capital and supervisory judgement.
Management can improve the ratio from either side
- retain earnings or raise Tier 1 capital;
- reduce balance-sheet exposure;
- allow short-term assets to mature;
- reduce some off-balance-sheet commitments;
- change financing structures where economically appropriate.
The bank should not optimise the ratio mechanically. Reducing economically useful, low-risk activity solely to improve a backstop can create other costs. The goal is a resilient balance sheet, not a beautiful number.
Why a backstop can improve confidence
Investors and supervisors know that risk weights can be wrong. An independent leverage measure provides another lens through which to judge capital strength.
When both risk-weighted and leverage measures are strong, confidence does not depend on one modelling architecture alone.
Stress testing gives the third view
Risk-weighted ratios ask how much capital the current measured risk requires. The leverage ratio asks how much broad exposure the capital supports. Stress testing asks what happens when the future becomes worse.
Article 44 completes this batch by pushing the bank through an adverse scenario instead of examining only today’s ratios.
Four misconceptions to remove
| Misconception | Better model |
|---|---|
| “The leverage ratio is total assets divided by equity.” | The regulatory measure uses Tier 1 capital and a defined exposure measure broader than simple accounting assets. |
| “It replaces risk-weighted capital ratios.” | It is a complementary backstop designed to catch excessive leverage when measured risk is low. |
| “Secured exposures do not matter because collateral removes risk.” | Collateral reduces loss risk but secured financing can still expand leverage and gross exposure. |
| “A strong leverage ratio proves the bank is safe.” | Liquidity, concentration, market risk, operations and future stress still require separate analysis. |
A mastery test
- Why does banking need a leverage-ratio backstop?
- Why is the denominator broader than accounting assets?
- How can low risk weights allow leverage to build?
- Why can the leverage ratio become binding for low-risk-heavy banks?
- Why should leverage, RWA and stress testing be read together?
If those answers connect, the leverage ratio becomes visible as prudential scepticism made numerical: even when models say risk is small, a very large balance sheet still needs enough real loss-bearing capital underneath it.