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st: RE: working out data structure


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: working out data structure
Date   Fri, 13 Aug 2004 12:36:55 +0100

In Stata terms each observation should be a pair of countries, 
e.g. Germany and France. Some values would necessarily be 
repeated e.g. the GNP value for Germany would be repeated 
for each pair that includes Germany. Merging transactions 
data files with country property files may be a good 
way to go. 

In some fields similar models are called gravity models. If 
Newton had had Stata, or indeed any other decent software, 
he would have been to regress 

ln Force_ij = b0 + b1 ln Mass_i + b2 ln Mass_j + b3 Dist_ij 

and discover that b3 ~ -2.  

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

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Armen
> Khachatryan
> Sent: 13 August 2004 11:33
> To: statalist@hsphsun2.harvard.edu
> Subject: st: working out data structure
> 
> 
> T. Otsuki report in Food Policy 29 (2004). The model they 
> suggest looks
> interesting also to my area. It looks like
>  
> ln(Vij)=b0+b1ln(GNPi)+b2ln(GNPj)+b3ln(POPi)+b4ln(POPj)+b5ln(DISTij)+
> b6*ln(MRL)+b7ln(100+TARIFF)+b8*Dbfa+b9*Dtacp+b10*Dntacp+b11*Dr
> est+b12*Drta+b
> 13*Dcolij+b14*D1997+b15*D1998+uij.
>          
>          Where i and j mean importing and exporting 
> countries, V denotes the
> value of trade from j to i. GNPs are clear, the same POPs, and DIST is
> distance  between i and j, MRL the max residue limit imposed 
> by i. TARIFF is
> applied tariff rate between i and j. The rest are dummies. 
> The data set
> covers 1997-1999.
>          
>          I have just started to consider doing something like 
> that. Surely
> one needs data. The data set structure is what I am concerned 
> with now. 
>          The problem I have is how to build the data set. 
> Unless I have the
> idea, I can't proceed with collecting the data.
>          Sorry for the lengthy writing, but I got a kind of 
> mental brake, I
> need help to move forwards.
>          Question(s):
>          In the data matrix should importing countries appear 
> horizontally
> and exporters vertically? How I fix the V, POP and others stuff for
> importers and exporters, how with distance.
>          Do you think it is ok to contact Mr. Wilson and Mr. 
> Otsuki (the
> author of the article mentioned above) asking them to send a 
> small piece of
> their dataset?
>          Any suggestion/help/hint will be very much appreciated.
>          
>          Thanks in advance.
>          
>          Armen
>          
>          
>          University of Hohenheim
>          Stuttgart, Germany
>          Tel.: +49 711 459 2600 or 3303
>          Fax: +49 711 459 3709 or 3762
> 
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