July 6th, 2006, 11:09 am
The phenomenon you describe is a well known behaviour in the CDO market. The implied correlation is not unique for mezz tranches, i.e for a contract with sensitivity towards the mid parts of the loss distribution there are two correlations which will produce the same price. An NtD with N > 1 can behave in this way.The reason for this will become obvious to you if you draw a graph of the loss distribution (number of defaults on the x-axis and number of occurrences, or the probability, on the y-axis). Make sure you understand what part of this loss distribution your contract is sensitive to. Draw the probability as the function of number of defaults for a range of correlations. You will see that your contract's area of interest in the graph will have the same size for two different correlations.Hope that helped.