[DDI-users] Documenting rates in the aggregate data extension

[Wendy Thomas]

This is a discussion I have had with Sanda as she was marking up the
Agriculture Census for us. The problem lies in the fact that the attribute
aggMeth is a fixed controlled list and "percent" is not one of the terms.
Ideally it should be and then there would not be a problem. Until this is
changed I suggested putting it into the measUnit, for example
measUnit="percent farms". Not elegant but it captures the information for
now and can be easily located in the event of a future update of the DTD

Wendy Thomas


On Tue, 9 Mar 2004, Humphrey Southall wrote:

> The DDI aggregate data extension is very clearly designed to document
> tables consisting mainly of frequency counts.  What should we do with
> pre-computed percentages?
>
> My project is converting existing machine-readable transcriptions of tables
> from British census reports to a structure which uses DDI-based metadata,
> and most of the columns in those tables are just such counts of numbers of
> people.
>
> They also contain columns which are pre-computed rates, generally
> percentages.  Most of them can be derived directly from counts held in
> other columns in the same table, and so far we have mostly ignored
> them;  we are not discarding them, as the system will also hold spreadsheet
> versions of the original tables, but they will not be easily located, or
> accessible to our visualisation tools.
>
> However, there are some rates in the reports which contain information not
> available in any other form.  The most immediate issue is with data in the
> main parish-level table from the 1951 census for England and Wales.  This
> includes population density, which can easily be computed from figures for
> population and area, and "Persons per Room", computable from the number of
> persons and the numbers of rooms in private households.  However, it also
> includes "Percentage of persons at more than 2 per Room".  Although another
> table gives plenty of information about numbers of people versus numbers of
> room, by household, for c. 1,500 districts from which this rate could be
> computed, no other information is available for the c. 15,000
> parishes.  The micro-data are official secrets until 2052, and as far as we
> can establish no unpublished intermediate calculations from pre-1971
> censuses survive anywhere -- so this is really interesting data.
>
> How can we include these data values in our system?  I can see that just
> about any number can be held in a non-additive nCube, but that greatly
> limits what we can do with it.  Is there another structure we should be using?
>
> Best wishes,
>
> Humphrey Southall
>                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     ====================================
> Humphrey Southall
> Reader in Geography/Director,
> Great Britain Historical GIS Project
> Department of Geography, University of Portsmouth
> Buckingham Building, Lion Terrace, Portsmouth PO1 3HE
>
> GIS Project Office: (023) 9284 2500
> Home office:  (020) 8853 0396
>
> Web site:	http://www.VisionOfBritain.org.uk
> About us:	http://www.gbhgis.org
>
> _______________________________________________
> DDI-users mailing list
> DDI-users at icpsr.umich.edu
> http://www.icpsr.umich.edu/mailman/listinfo/ddi-users
>

Wendy L. Thomas                          Phone: +1 612.624.4389
Data Access Core Director		 Fax:   +1 612.626.8375
Minnesota Population Center              Email: wlt at pop.umn.edu
University of Minnesota
537 Heller Hall
271 19th Avenue South
Minneapolis, MN 55455