As Orwell's Room 101 beckons for LIBOR publication, muRisQ Advisory's Marc Henrard warns of potential pitfall in the fallback protocol.
This is the Risk.Net introduction to Marc's comment about the cleared/uncleared fragmentation of the market due to the design of the IBOR fallback.
The full text is available on Risk.Net website (subscription required):
Figure from the above published comment.
Note that the issue of the market fragmentation will be particularly visible in EUR where it is expected that EUR-LIBOR will be discontinued at the end of 2021 and EUR-EURIBOR will continue to exist probably for a further 5 years. It appears that the EUR-LIBOR fallback will be done directly to ESTR and not to EUR-EURIBOR as suggested in our answer to the ISDA EUR fallback consultation. Any payment originating from LIBOR fallback will be easy to compare to an actual EUR-EURIBOR payment (see also the post about the EUR curve shape not in line with ISDA fallback at all).
The discrepancy between fallback contaminated and clean versions of LIBOR payments should be taken into account in bond reference rate switch from LIBOR to SONIA. A popular method seems to infer the adjustment spread for bonds from the swap market as reported in Nationwide and Lloyds win nod for Sonia bond switch (subscription required). But those spreads are based on the historical past spread, not on the forecast of actual LIBOR-like value. Obviously the switches have been done with the approval of the note-holder, but was that approval based on a clear understanding by the note-holders of what was behind those contaminated cleared swap market figures?