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st: Data Manipulation--is the merge command appropriate?


From   "Asiedu, Elizabeth" <asiedu@ku.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Data Manipulation--is the merge command appropriate?
Date   Mon, 25 Sep 2006 10:12:47 -0500

I have an unbalanced panel dataset. I'd like to convert to a balanced panel dataset where the data for the missing years are zero. How do I do this in Stata? I'll use an example to illustrate my problem.

 

 

Dataset 1

Country id        year                  foreign aid

1                      1993                230

1                      1994                130

2                      1990                100

2                      1994                120      

 

There are 2 countries. Country 1 did not receive any aid for 1990,1991, and 1992. Country 2 did not receive aid for 1991, 1992 and 1993. I'd like each country to have data from 1990-1994, and for foreign aid=0 for the missing years. 

 

 

The dataset I need for my analysis should look like

 

Dataset 2

Country id        year                  foreign aid

1                      1990                0

1                      1991                0

1                      1992                0

1                      1993                230

1                      1994                130

2                      1990                100

2                      1991                0

2                      1992                0

2                      1993                0

2                      1994                120

 

 

This is what I tried. 

Step 1: I created another dataset with only two columns; country id and year:

 

Dataset 3

Country id        year                  

1                      1990                

1                      1991                

1                      1992                

1                      1993                

1                      1994                

2                      1990                

2                      1991                

2                      1992                

2                      1993                

2                      1994                

 

Step 2: I merged the two datasets (i.e., Dataset 1 and Dataset 3) using country id and year.

 

I thought the merge will generate a balanced panel with "null" values for the variable foreign aid, for the years for which the country did not receive any aid. I could then replace the "null" with zeros. However the merge did not produce the desired result-it just did not work.  

 

Any suggestions? Is the merge command appropriate?

 

Thanks in advance.

 

Elizabeth Asiedu


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