nested logit: degenerate and dissimilarity parameter

[Mina Sami]

I made a Nested logit model. Level 1: 8 choices and level 2: 22 choices.
In type 4, I have only 1 choice in level 1 corresponds to one choice in level 2.

The dissimilarity parameters are equal to 1 in this case (not surprising).

Can i run the model normally when i have a an IV parameter than is equal to one?
The results can be interpreted normally or what should i have to do in this case?

I tried the commande "constraint 1=[type4_tau]_cons=1" but the model does not run.

what can i do?

Thanks in advance for your advices

[Roberto Santos]

I am working with this kind of model now, and there is some theoretical literature on that here. For an application, take a look here. I don't have an answer for the command part of the question, but I know that the dissimilarity parameter for the degenerate nest should be set to 1.