(19)Pursuant to Article 171(2) of Regulation (EU) No 575/2013, the less information an institution has, the more conservative its assignment of exposures to obligor and facility grades or pools needs to be. The assignment of securitised exposures to grades or pools is thus of particular concern when using proxy data. That is even more relevant where there is a difference between the definition of default used by the institution calculating K IRB in its internal model for calculating K IRB and the definition of default used in the external data corresponding to the securitised exposures, to the portfolio underwritten on the basis of similar underwriting standards of the originator or original lender from which they have been extracted, or to the proxy data. It is therefore necessary to lay down rules about the adjustments to be made in the data, and about the margin of conservatism to be adopted when estimating the risk parameters in the context of calculating K IRB for qualifying securitised exposures.