Calculate Weighted Aggregation between Two Tables

Hi,

I have global national statistics (GDP, Fish Catch etc.), which I
would like to aggregate to and calculate per Capita data for given
regions (Africa, Europe...) and subregions (Western Africa, ....) on-
the-fly.

From a statistical point of view it seems best to use something like
this:

given that the variable is "v" and the Total Population table is
"tp":

(country_1_of_region_1_for_v / country_1_of_region_1_for_tp) +
(country_2_of_region_1_for_v / country_2_of_region_1_for_tp) + ....

------------------------------------------------------------------------
------------------------------------------------------------------------
---------------------------------------

(sum_countries_all_of_region_1_for_v /
sum_countries_all_of_region_1_for_tp)

and then same thing for the other regions (in my case a total of
6 regions).

I have a table of countries with a field country_id and region_id
(which specifies to which region this country belongs).
I have the table for the variable with a field country_id, which has
kind of a "Excel design", i.e. columns for each year.
And I have a table of regions with a field region_id.

It seems like a rather complicated thing to do, as one needs first to
get all the countries of a specific region for both tables (variable
& pop_total), have the SUM(of all countries) available and run the
mathematical procedure...

Could someone give me a hint how this could be achieved?

Thanks for any help!

Stef

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Stefan Schwarzer

Nature Photography: http://photoblog.la-famille-schwarzer.de
UNEP GEO Data Portal: http://geodata.grid.unep.ch
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