In short, I estimate 4 probit regressions, examining the effects of a variable X on the probability of being employment (versus unemployed), on 4 worker groups:

1. total sample
2. sector a
3. sector b
4. sector c.

In each model the command is the same:

dprobit employed X

and all the estimations are successfully carried out.


Then I try to incorporate all 4 regressions in 1, i.e. estimate a multinomial probit model.

In this case I examine whether variable X affects mobility between these sectors a, b and c, using an indicator variable taking the values 1, 2 and 3, respectively.

The command use is:

mprobit id X

However, in all my attempts the model cannot estimated. The results either indicate "Hessian not negatively semi-definite" or the iterations (not concave) just continue for ever.

May someone explain to me how comes the probit models are estimated without problems, but the multinomial probit model not? Using the same data set?

Are there any ways to solve this?