Re: st: mlogit coefs

[Maarten Buis <maartenlbuis@gmail.com>]

Sounds like a (minor or large) violation of the IIA assumption.

-- Maarten

Ps. I know I am not explaining a lot here. I just give you the
relevant key word for you to search.

On Tue, Apr 17, 2012 at 4:00 PM, Chiara Mussida wrote:
> Dear All,
> I run a mlogit model for 9 labour market outcomes (transitions between
> the three states of employment unemployment and inactivity, therefore
> 6 transitions and 3 permanences), like:
>
> mlogit transition male_unmarried female_married female_unmarried age
> agesq ncomp child northw northe centre Ubenef edu1 edu2 health
> qu1nolav qu3nolav qu2nolav nopersincnolav noothersineq qu1ot qu2ot
> qu3ot if age>=15 & age<=64, b(3)
>
> the baseline category is the permanence in the state of unemployment.
> If I decide to run my mlogit only on the subsample of unemployment,
> thereby reducing the number of outcomes to 3:
> mlogit unemployedmale_unmarried female_married female_unmarried age
> agesq ncomp child northw northe centre Ubenef edu1 edu2 health
> qu1nolav qu3nolav qu2nolav nopersincnolav noothersineq qu1ot qu2ot
> qu3ot if age>=15 & age<=64, b(3)
>
> and keeping the permanence in the unemployment as baseline, I get
> different coefficients signs and significance for a dicrete amount of
> covariates, e.g. female_unmarried. My question is: I know that the
> first mlogit refer to a larger sample that includes all the labour
> force, whilst the second one only refer to the subsample of
> unemployed, but this is enough to justify the different behaviour of
> the coefs?
>
> The choice to use the "extended" mlogit (9 outcomes) is related to
> sample selection issues. SInce I have data to all the labour force it
> is better to consider all of them and to avoid an ex ante selection
> (and likely a selection bias).
>
> Thanks,
> Chiara
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-- 
--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany


http://www.maartenbuis.nl
--------------------------

*
*   For searches and help try:
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*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/