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st: Summation & variable Creation


From   Socrates Mokkas <socrates.mokkas@economics.oxford.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   st: Summation & variable Creation
Date   Tue, 17 Oct 2006 17:39:36 +0100

Hi,

Below is a part of my sample. Note that i and j refers to Co_ids (Company ids) and that each Co_id belongs into a single Sh_id (Shareholder).

Year  Co_id  Tax   TA   Sh_id 
2004    A    .4    12   1
2004    B    .5    11   1
2004    C    .2     2   1
2004    D    .4     5   2
2004    E    .6     7   2
2003    A    .3     9   1
2003    B    .1     .   1
2003    C    .4     1   1
2003    D    .7     8   2
2003    E    .6     9   2

I need to create two variables for each Co_id {A, B, C, D and E):
The 1st one should equal to r(i)=TA(i)/[SumTAs], where i=A, B, C, D and E. Hence, Co_id(A) should be equal to 12/(12+11+2) for year 2004 and "." because one of the Co_ids owned by the same Sh_id has a missing value in each TA.

The 2nd veriable is much more involved. I want to create a variable that is equal to:
the Sum(across j) of [Tax(i)-Tax(j)]r(j). For 2004 and Co_id A should be:
[Tax(A)-Tax(B)]*r(B)+[Tax(A)-Tax(C)]*r(C)=[0.4-0.5]*r(B)+[0.4-0.2]*r(C). For B it should be [0.5-0.4]*r(A)+[0.5-0.2]*r(C). Similarly, this variable should give "." if one of the arguments for one of the Co_ids is not there.

Thank you very much.

Regards,
Socrates



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