I am getting old.Alas it is many years since I've been in a trading room but I still have to help people with Finance. I'm currently teaching US MBS. I recall that there was no consensus around OAS models as recently as five years ago. The differences revolved around the two components?The pre-payment models - some were econometric while others attempted some form of adjusted risk-neutral optimal option exercise. I don't know whether one approach is more popular than the other, or whether there has been a move towards a single model. The interest rate model used to generate used to generate the simulated paths.My guess is that there is still a lot of variability between the OAS models used by different firms, but I could be out of date. I understand that the Bloomberg model is widely used, but has it become some kind of market standard?It used to be that the different models made relative value assessments fairly opaque. In some cases the models might agree, but elsewhere a cheap bond could turn into dear according to the model. Is this still true?All help gratefully receivedOld and fat.