st: fractional response using xtgee - correct implementation of random effects and fixed effectst?

[Asmund.Rygh@bi.no]

(First line)

Dear Statalist members,

I would like to model the degree of internationalization of firms (a 
fractional variable bounded between 0 and 1) using a strongly balanced 
panel of 30 firms over an 11-year period, and test both the use of fixed 
and of random effects. I am using Stata 12.

I have read Papke and Wooldridge's (2008) article Panel data methods for 
fractional response variables... (see 
http://www.sciencedirect.com/science/article/pii/S030440760800050X) and 
consulted the archives of Statalist. I found one relevant thread from 2012 
at http://www.stata.com/statalist/archive/2013-06/msg00517.html as well as 
a very recent one (last post 12 June) at 
http://www.stata.com/statalist/archive/2013-06/msg00434.html which does 
not appear to have been answered yet.

In the first link from 2012 it is suggested to go to the website of Leslie 
Papke at https://www.msu.edu/~ec/faculty/papke/papke.html where one "would 
find lots of invaluable information with detailed codes as to how 
implement in case of panel data". Perhaps, the answers to my question 
could be found here. However, I am not able to access this site and the 
following message is returned: You don't have permission to access 
/~ec/faculty/papke/papke.html on this server. Thus, my first question is 
simply whether somebody knows if I can access the material in Papke's 
webpage from somewhere else? I have made extensive searches on the web but 
couldn't find anything.

To my main question: From the discussion in the above threads (as well as 
my experience with using random effects and fixed effects in Stata for 
normal variables), I am sort of guessing that the following two commands 
using -xtgee- will achieve what I want:

Random effects: xtgee dependent_variable independent_variables, 
family(binomial) link(logit) vce(robust)

Fixed effects: xtgee dependent_variable independent_variables 
time_averages_independent_variables, family(binomial) link(logit) robust

In the first case, I set firm and year as the panel variables (-xtset-) 
and the output states that the group variable is firm. In the second case, 
which I did not test yet, my interpretation of the discussion in PW2008 
(see p. 123) and at the above mentioned links is that including time 
averages will give me the fixed effects. Is this correct?

Thank you for your time.

Best,
Asmund Rygh


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