Why does regulatory capital target unexpected loss and not expected loss?

Question

AcadiFi · Accepted Answer

The separation between EL and UL is a foundational principle of modern capital frameworks, reflecting different economic purposes of provisions versus capital.

**Provisions (for EL):** Loan loss reserves are the accounting mechanism for recognizing expected credit losses. Under IFRS 9 / CECL, banks book provisions based on lifetime or 12-month expected losses depending on stage. Provisions are funded from net interest margin — the credit spread charged borrowers includes a component covering PD × LGD × EAD. Effectively, EL is a normal cost of lending, like operational expense.

**Capital (for UL):** Capital protects against losses that exceed the normal expectation — tail events, correlated defaults, severe downturns. Capital is shareholders' money at risk, expected to earn a higher return than debt because it absorbs the volatility.

Double-counting would occur if capital covered EL too: the credit spread already compensates for EL, and provisions are already set aside. Asking capital to also cover EL would over-capitalize banks.

```mermaid
flowchart TD
  A[Total credit loss] --> B[Expected EL]
  A --> C[Unexpected UL]
  B --> D[Priced in spread]
  D --> E[Booked as provisions]
  C --> F[Tail of loss dist]
  F --> G[Capital absorbs]
```

Basel III finalization reinforced this by requiring the 'provision shortfall' — amount by which IRB EL exceeds accounting provisions — to be deducted from CET1. This ensures the EL portion is always covered by either provisions or capital, never neither, but avoids counting EL twice in capital requirements.

Westmoreland Bank with $500M portfolio EL $8M and provisions $6.5M must deduct the $1.5M shortfall from CET1, preserving the EL-UL separation.

Why does regulatory capital target unexpected loss and not expected loss?

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