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 filesinfo@statssa.gov.za www.statssa.gov.za

EA / PN & SA Spatial/geographic enquiries & comments

helenev@statssa.gov.za