1. In quantifying the risk parameters to be associated with rating grades or pools, institutions shall apply the following requirements specific to PD estimation to exposures to corporates, institutions and central governments and central banks and for equity exposures where an institution uses the PD/LGD approach set out in Article 155(3):
(a) institutions shall estimate PDs by obligor grade from long run averages of one-year default rates. PD estimates for obligors that are highly leveraged or for obligors whose assets are predominantly traded assets shall reflect the performance of the underlying assets based on periods of stressed volatilities;
(b) for purchased corporate receivables institutions may estimate the EL by obligor grade from long run averages of one-year realised default rates;
(c) if an institution derives long run average estimates of PDs and LGDs for purchased corporate receivables from an estimate of EL, and an appropriate estimate of PD or LGD, the process for est
…