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RE: AW: st: maximum number of outcomes in mlogit


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: AW: st: maximum number of outcomes in mlogit
Date   Wed, 21 May 2008 11:38:27 +0100

Discussion has focused on the question of whether this is sensible or
desirable. 
My gut has been in perfect resonance with those of Maarten and Jay on
this, but just 
voting for that point of view won't make it stronger. 

The direct answer to the question appears to be that a limit of 50
outcomes is wired into -mlogit-, or more precisely -_mlogit-. So, unless
StataCorp change it, or you clone -_mlogit-, the answer is No. 

I have no inside knowledge on this detail, but it wouldn't surprise me
if that limit was based on simulations showing how far -mlogit- can
deliver credible and intelligible results in reasonable time. StataCorp
would want to protect users, and themselves, from results that were not
defensible. That is the sort of thing they do a lot of. 

Nick
n.j.cox@durham.ac.uk 

Tiemann, Michael

>Maarten asked:
>Are you aware that there are already many clasifications and scales of
occupations? 
Yes, I am fully aware of that. I work for the federal institute for
vocational education and training. 

>I realize that you are not going to like the following statement, but I
don't see much reason to reinvent yet another clasification. 
The thing is that existing classifications cannot aggregate occupations
in the way we need them to be aggregated. We need tasks to primarily
define groups of occupations, which nominally the KldB92 and 88 follow.
But they are not consequent: besides tasks there are a number of
different criteria used for classifying. If this wasn't the case we'd be
happy to use these classifications.

>For instance, take a look at -findit isko- and -findit isco- for some
Stata implementations of some existing scales and clasifications.
The thing with isco is that we want to use qualifications (ie skills
level here) not to classify occupations but to find out whether they
might change over time for a given set of occupations. 

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