st: Mfx after zero-inflated (ZOIB) estimator

[Alexandros Zangelidis <a.zangelidis@gmail.com>]

Dear STATAList users,

I’m writing regarding the zero-one inflated beta distribution (ZOIB)
estimator (as available from SSC). I’m currently using this estimator
in a model of sickness absence in order to separate the process that
determines (a) the decision of being absent (binary decision), from
(b) the level of sickness absence from work  (proportion of contracted
hrs).

After the estimation of the model using ZOIB and estimate the marginal effects:
•	mfx, predict(pr0)
•	mfx, predict(prcond)

I was wondering whether you could help me understand how exactly the
marginal effects are calculated (formula) and how comparisons can be
made to the marginal effects in a standard probit/logit. For example
are the marginal effects for each binary explanatory variable
calculated by fitting two separate probability functions? Exactly how
are the marginal effects for the continuous variables calculated?
Looking forward to hearing from you,

Kindest regards,

Alexandros

Dr. A. Zangelidis | Lecturer in Economics | University of Aberdeen |
Scotland | UK

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