Constraining all coefficients to be equal, mlogit, Stata

Question

I have a multinomial logit model that I want to estimate with mlogit. I want to constraint the coefficients on one of the independent variables (but not the rest) to be equal across all alternatives. I have tried the following constraints, but always get an error from Stata, "constraint number # caused error r(198))":

constraint define 1 [1=2]var_name  
constraint define 2 [1=3]var_name  
constraint define 3 [1=4]var_name  
constraint define 4 [1=5]var_name

OR

constraint define 1 [1]var_name = [2]var_name  
constraint define 2 [1]var_name = [3]var_name  
constraint define 3 [1]var_name = [4]var_name  
constraint define 4 [1]var_name = [5]var_name

There are 6 alternatives total, I use the 6th as base. Any help would be much appreciated.

dimitriy dimitriy · Accepted Answer · 2014-06-19T20:32:45

Try something like this:

webuse sysdsn1
tab insure
constraint 1 [Prepaid]age=[Uninsure]age
mlogit insure age male nonwhite i.site, base(1) constraint(1)

Constraining all coefficients to be equal, mlogit, Stata

1 Answers