Basel Correlation Assumptions for Qualified Revolving Retail

Summary

The document asks why Basel credit risk formulas assign qualified revolving retail exposures a lower asset correlation than other retail exposures. It presents the other-retail correlation as a probability-dependent function and contrasts it with a fixed, lower correlation for qualified revolving exposures over the stated probability range. The author seeks an economic interpretation of the regulatory distinction, especially why the relationship between default probability and broad economic sensitivity might differ from the corporate case.

The text offers the formula and frames questions about portfolio credit risk, but it does not provide an answer, empirical evidence, or a derivation of the assumptions. Consequently, it is most useful as a statement of the Basel modeling issue rather than a guide to applying the formulas. Any interpretation would need to consult the relevant regulatory framework and supporting evidence about how these exposure classes behave across economic conditions.

Key ideas

• Basel retail risk weights depend in part on assumed correlation between borrower defaults and the economy.
• The other-retail correlation varies with probability of default under the formula shown.
• Qualified revolving retail is assigned a fixed lower correlation in the comparison described.
• The document raises, but does not resolve, the economic rationale for this classification.

Tags

# Why do supervisors deem qualified revolving retail less risky than other retail exposure


# Why do supervisors deem qualified revolving retail less risky than other retail exposure












I would like to gain more understanding of the economic background of some Basel formulas. In the Basel guidelines in retail credit risk we have a risk weight function that depends on the correlation of the debitor's default to the broad economy.

For "other retail" it looks like this:

$$ R = 0.16 - 0.14 \frac{1-e^{-25 pd}}{1-e^{-25}} $$

For qualified revolving (QR) it is fixed at $0.04$ and therefore gives lower correlation for pds below 7%.

To get a better intuition to these formula and quantiative analysis that follow from it I would like to discuss:

- what typical nature of QR retail exposure makes it less risky than other retail exposure?

- while I can understand the logic that low pds are more (!) correlated to the broad economy for corporates - what is the argument for retail here?

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