[Limdep Nlogit List] Is a multinomial logit model with selection applicable here?

[Haab, Timothy]

James, looks like you will need a nested model (logit?) with the top level nest being trip/no trip, and then conditional on trip, mode.  

-----Original Message-----
From: limdep-bounces at mailman.sydney.edu.au <limdep-bounces at mailman.sydney.edu.au> On Behalf Of James Giller via Limdep
Sent: Tuesday, February 15, 2022 4:20 PM
To: limdep at mailman.sydney.edu.au
Subject: [Limdep Nlogit List] Is a multinomial logit model with selection applicable here?

Hi,

My dependent variable is based on travel mode choice survey data, and it has a value for "make no trip at all" as well as values for various modes, car, transit, taxi, walking, etc. The mode is only observed if the survey participant would make a trip, which made me consider a sample selection model.

My dependent variable Y has the following values:
0 = transit
1 = car
2 = carpool
3 = taxi
4 = walking
5 = other
6 = no trip

I created another variable DOTRIP, which is 0 if Y = 6, and 1 otherwise.

I then tried to estimate the following model PROBIT ; Lhs = DOTRIP ; Rhs = <explanators> ; Hold $ MLOGIT ; Lhs = Y ; Rhs = <explanators> ; Selection ; Pts = 25; Halton $

The above model on the data set as explained returned an error message that there is insufficient variation in the dependent variable during the MLOGIT part. I think this is because the value 6 (no trip) is possible for Y, but none of the observations would be selected in the selection step.

Am I correct in specifying a model with sample selection in this case? Or should I take a different approach to account for the individuals first deciding whether or not to travel, then by which mode?

Is there some way to rearrange my data so that the above model will work?

Thank you.
James.
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