st: on balancing a panel data

[rado645-bg@yahoo.de]

Dear all,

I have a panel data set of observations for countries over several years. The 
number of countries varies: the minimum number  is 52 per year and the maximum 
number is 73. For certain reasons (graphs),  I would like to make the panel 
dataset a kind of balanced and I need to have the same countries in each year 
across the sample period even if I would need to exclude some of them.

Could you help me on how one can make this in Stata, i.e. to keep only those 
countries for which data is available for each year and exclude the rest. Below 
is a simplified description of the dataset:

year      country    var1
1990     1              ...
1990      2             ...
1990      3             
1991     1
1991     2
1992     1
1992     2
1992    3
1992    4
1992    5
1993    1
1993    2
1993    5
...




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