As part of the default risk charge (DRC) in the internal models approach (IMA) within the Fundamental Review of the Trading Book (FRTB), the Basel Committee on Banking Supervision (BCBS) has set a floor of 3 basis points (bp) for the probability of default (PD) of any entity. This input floor applies to all entities and primarily impacts the highest rated AAA sovereigns.

There has been no evidence published to date to support the calibration of the 3 bps floor and as local jurisdictions implement FRTB, some jurisdictions have already published their intentions to adjust this floor.

This paper provides quantitative and qualitative analysis in support of the removal of the PD floor. The paper uses the Bayesian inference model to estimate the probability distribution of rare events (eg, defaults of highly-rated entities) and sensitivity analysis is performed to demonstrate its robustness.