ms h verhoef isibalo symposium, free state october 11, 2013
TRANSCRIPT
WORKING TOWARDS OPTIMAL DISSEMINATION GEOGRAPHIES
FOR CENSUS 2011
Ms H VerhoefIsibalo Symposium, Free StateOctober 11, 2013
Introduction
• Literature study
• Needs assessment
• Evaluation of 2001 output geographies
• Recommendations and specifications for the 2011 small area design
Why does geography matter?
Geography:• Where?• Spatial relationships and distribution
• Visualisation
Nested hierarchy for the South African census of 2011
Census geography
• Enumeration Areas – Collection geographyo Designed to manage fieldworko Homogeneity according to
residential type or land use – EA type
Census data• Aggregated on different geographic levelso Generalisation o Loss of detail
•Modifiable Areal Unit Problem
MAUP illustrated
Source: www.zonedesignsystems.com/intro4 The Modifiable Areal Unit Problem/Zone Design Systems.
Enumeration Area Population RangeTotal Population Range Number of 2011 EAs %
0 7115 6.9
1 to 10 2206 2.1
11-100 6151 5.9
101-200 5842 5.6
201-300 7555 7.3
301-400 9950 9.6
401-500 12824 12.4
501-600 14875 14.4
601-700 13033 12.6
701-800 8802 8.5
801-900 5632 5.4
901-1000 3375 3.3
1001-2000 5876 5.7
>2001 340 0.3
Total 103576 100.0
Output geography
• What are other countries doing?
• Problem with 2001 output geographyo Very large physical areaso Island EAs/SAs
The problem with SA’s current output geography
Outcome of SAs’ user needsCensus variables Ave score Rank
Total population 8.3 1
Housing 8.1 2
Total Households 8.0 3
Employment / unemployment 7.5 4
Education 7.5 5
Income 7.3 6
Water 7.1 7
Energy 7.1 8
Sanitation 7.1 9
Population Group 7.0 10
Age Groups 6.8 11
Gender 6.4 12
Goods & Services 5.8 13
Agriculture 5.6 14
Language 5.3 15
Citizenship 5.3 16
Migration 5.2 17
Mortality 5.0 18
Parental survival 4.3 19
Two options for input in the creation of small areas for 2011
• EAs:
Inherit EA demarcation specifications and problems
• Geo-coded record data:
Not all 2011 records were geo code-able to addresses or smallest land parcels
Create building blocks such used in the UK or Canada ?
Options for the output geography design
Same specifications as 2001 SAL - Same problems
Same specifications as 2001, except change population minimum from 500 to 300
- Potentially better (but still island problems)Change specifications:
- Find ideal tot pop within confidentiality frame
- Test for the most wanted variables
Options for the output geography design (continue)Re-demarcate the vacant areas to eliminate all
island EAs and limit physical size when merging EAs
- potentially better shapes and area size
Exclude vacant and populated areas with population below 10
- potentially better shapes and areas size
NB: This option will result in non-contiguous coverage – suppressed areas blank
Census 2011 Small AreasAs many as possible SAs = one EA, depending on the EA population size and acceptable level of confidentiality.
The small areas should ideally be:as small as possible in terms of physical area
and population size,as compact in shape as possible,as homogeneous as possible (EA type),fall within administrative boundaries.
South African hierarchiesSOUTH AFRICA 2011
Province
SA by
Municipality
SA by Electoral Ward
SA by Magisterial District*
SA by Province and Magisterial District*
SA by Province and Municipality
District Council or Metro
District Council or Metro
Magisterial District*Magisterial District*
District Council or Metro
Municipality:* Metro* Local Municipality
Municipality:* Metro* Local Municipality
Municipality:* Metro* Local Municipality
Electoral Ward
Main Place
Sub Place:Suburb /Section / Sub-Village / NU
Main PlaceCity / Town /
Township / Village / NU
Enumeration Area
Suburb /Section / Sub-Village / NU
Sub Place
City / Town / Township / Village /
NU
Magisterial District* - could be any other geography such as traditional areas / health districts / catchment areas, etc
Small Area Layer
Future research & developmentCreation of new building blocks
Blocks or block-faces similar to what is done in Canada or the postman walks in the UK Useful to create all other areas such
as wards, voting districts, policing areas etc.
Sample framesComplete the address frame
Enable us to link census questionnaires to localities in stead of EAs
Create unique user determined output
Census data, publications and spatial [email protected] www.statssa.gov.za
EA / PN & SA Spatial/geographic enquiries & comments