HSBC 2012 Annual Report Download - page 299

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implementation, assuming there were no major changes in the portfolio from the testing phase to implementation
phase.
Portfolios moving onto IRB approach
Where a portfolio moves from the standardised approach to the IRB approach, the RWA movement by key driver
statement shows the increase in IRB RWAs, but does not show the corresponding reduction in standardised approach
RWAs as its scope is limited to IRB only.
The movement in RWAs is quantified at the date at which the IRB approach is applied, and not during the testing
phase as with a new/updated model.
4. Methodology and policy
Internal updates
This captures the RWA impact resulting from changing the internal treatment of exposures. This may include, but is
not limited to, identification of netting and credit risk mitigation.
External updates
This specifies the impact resulting from additional or changing regulatory requirements. This includes, but is not
limited to, regulatory-prescribed changes to the RWA calculation. The movement in RWAs is quantified by
comparing the RWAs calculated for that portfolio under the old and the new requirements.
5. Book size
RWA movements attributed to this driver are those we would expect to experience for the given movement in
exposure, as measured by EAD, assuming a stable risk profile. These RWA movements arise in the normal course of
business, such as growth in credit exposures or reduction in book size from run-offs and write-offs.
The RWA movement is quantified as follows:
• RWA and EAD changes captured in the four drivers above are excluded from the total movements to create an
adjusted movement in EAD and RWA for the period.
• The average RWA to EAD percentage is calculated for the opening position and is applied to the adjusted
movement in EAD. This results in an estimated book size RWA movement based on the assumption that the
EAD to RWA percentage is constant throughout the period.
As the calculation relies on averaging, the output is dependent upon the degree of portfolio aggregation and the
number of discrete time periods for which the calculation is undertaken. For each quarter of 2012 this calculation was
performed for each HSBC company with an IRB portfolio, split by the main Basel categories of credit exposures, as
described in the table below:
Basel categories of IRB credit exposures within HSBC
Central governments and central banks Corporate foundation IRB Qualifying revolving retail exposures
Institutions Other advanced IRB Retail SME
Corporate advanced IRB Retail mortgages Other retail
The total of the results is shown in book size within the RWA movement by key driver table.
6. Book quality
This represents RWA movements resulting from changes in the underlying credit quality of customers. These are
caused by changes to IRB risk parameters which arise from actions such as, but not limited to, model recalibration,
change in counterparty external rating, or the influence of new lending on the average quality of the book. The
change in RWAs attributable to book quality is calculated as the balance of RWA movements after taking account of
all drivers described above.
The RWA movement by key driver statement includes only movements which are calculated under the IRB
approach. Certain classes of credit risk exposure are treated as capital deductions and therefore reductions are not
shown in this statement. If the treatment of a credit risk exposure changes from RWA to capital deduction in the
period, then only the reduction in RWAs would appear in the RWA movement by key driver tables. In this instance,
a reduction in RWAs does not necessarily indicate an improvement in the capital position.