st: Computing Herfindahl-Hirschman index

[Syed Basher <syed.basher@yahoo.com>]

Dear Statalist,

I have the following (hypothetical) trade dataset which contains imported items by importer.

importer  | item1 item2..... item20
-----------------------------------
11        |  10      20        80 
12        |   5       7         9 
13        |           1        
14        |   2                 6
...       |
20        |   8       9

I would like to obtain the following table/data: 

importer  | item1      item2   .... item20
-------------------------------------------
11        |  1600     2921.84       7091.41 
12        |   400      357.92         89.75
13        |              7.30        
14        |    64                     39.88
...       |
20        |  1024      591.67


where, say, the value 1600 is obtained using the formula (si*100)^2, where si is the share of importer11 in item1 and is obtained using 10/25,   25 is the sum of all entries in item1. This will allow me to get the  Herfindahl-Hirschman index by importer for each item.

I hope any one of you can help. Thank you so mcuh.

Regards,

Syed Basher
Qatar National Food Security Program


      

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