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OLS Regression, dummy variables issue

Posted: Sun Apr 01, 2012 3:57 am
by edj1991
Hi,

I am trying to estimate a simple growth regression to try to find a positive impact of mobile penetration on average growth rates in african countries. I can estimate the OLS however I am trying to include dummy variables for each country (-1 for reference). When I include all variables plus dummies for each country EVIEWS gives me the message 'insufficient number of observations'. Can anyone shed some light/offer some advice as to why this is happening? As when I run the regression without dummies I can get an output.

Thanks

Re: OLS Regression, dummy variables issue

Posted: Sun Apr 01, 2012 7:15 am
by startz
You can't have a dummy for each country when you only have one observation for each country.

Re: OLS Regression, dummy variables issue

Posted: Mon Apr 02, 2012 2:40 am
by edj1991
so dummy variables being used here is useless? I was doing this based on advice from a tutor. Perhaps she did not understand my specification.

Re: OLS Regression, dummy variables issue

Posted: Mon Apr 02, 2012 6:22 am
by startz
Not useless, impossible.

Re: OLS Regression, dummy variables issue

Posted: Mon Apr 02, 2012 6:27 am
by edj1991
However dummies for say country regions (eg. northern africa) would work here?

Re: OLS Regression, dummy variables issue

Posted: Mon Apr 02, 2012 7:01 am
by startz
Mechanically, yes that would work. You might ask why dummy variables should be used here. For that matter, you might ask why cell phone penetration causes GDP growth rather than the other way around.

Re: OLS Regression, dummy variables issue

Posted: Mon Apr 02, 2012 8:18 am
by edj1991
as there may be significant differences amongst different nations within Africa, as some as upper middle income countries whereas many are low income countries. Yes there is the possibility/likelihood of endogeneity, reverse causality. My problem is that I have tried to replicated a similar specification to those used in the relevant literature however my coefficient for mobile penetration is coming out as negative.