st: Weighted summing in a loop for members of a group

[Timm Klare <timm.klare@gmail.com>]

Hello everybody,

I would appreciate your help in solving the following problem. I work
on a dataset containing balance sheet and other information about a
couple of million European companies (AMADEUS).  The data relevant to
my current problem is made up of the following variables:

GROUP_PARENT    NUM_ID    YEAR    TOTAL_ASSETS    GROUP_TOTAL_ASSETS    TAXRATE

NUM_ID is the unique ID of each company and GROUP_PARENT is the ID of
the parent company for each group of companies. For each NUM_ID and
YEAR I need to calculate an new variable. It should sum the
asset-weighted tax rate differences between each NUM_ID YEAR and all
other companies in each group:

(sigma sign) (TAXRATE[NUM_ID] – TAXRATE[i])*(TOTAL_ASSETS[i]/GROUP_TOTAL_ASSETS)

Where i corresponds to all other companies in the observed group.
How can this be done? Is there a “sigma sign” like summing function in
STATA? I tried using a foreach loop but failed.

Thanks for your consideration
Timm

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