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Proc MDC, nlogit: Nest Statement Contains Redundant Choices for the level 1

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Proc MDC, nlogit: Nest Statement Contains Redundant Choices for the level 1

Hi All.

I am attempting to estimate a nested logit model using the MDC procedure. I have run a conditional logit model using the following proc mdc statement, which works fine:

proc mdc data = base outest = ests type = clogit;

model decision = x1 x2 x3... x15 /

  choice = (plan 348 341 ...);

id consumer;

run;

I truncate the list of alternatives because it is huge. I would like to allow for correlation among the error terms for two types of products over which I estimate choice probabilities, so I next specify a 2-level nested logit model where the first level is the choice of type1 v. type2 and the second is choice among alternatives within type1 and type2. I do this as follows:

proc mdc data = base type = nlogit;

model decision =x1 x2 x3... x15  /

  choice = (plan 347 341 ...);

id consumer;

utility u(1,) = x1 x2 x3... x15;

nest level(1) = (347 341... @1, 344 0 ... @2),

level(2) = (1 2 @ 1);

run;

When I submit this statement I see the following error:

Warning: NEST statement contains redundant choices for the Level 1. See 1st MODEL statement.

I'm quite unsure what this means- I believe I've specified everything correctly, and i know for a fact that in the nest statement there are no alternatives that are in both the @1 and @2 levels which is how I'm interpreting the error.  Any advice or insight would be greatly appreciated.

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