Providing Access to Census-Providing Access to Census-based Interaction Data in the UK: based Interaction Data in the UK:

That’s WICID! That’s WICID!

John Stillwell

School of Geography, University of Leeds

Leeds, LS2 9JT, United Kingdom

Presentation at the Third International Conference on Computing, Communications and Control Technologies (CCCT '05)

Austin, Texas, July 24-27, 2005

PresentationPresentation

• UK Census interaction data

• The WICID system

- Building queries in WICID

- Output and analysis in WICID

• Mapping and analysis

• Conclusions

UK Census interaction dataUK Census interaction data

• Since 2002, Census Interaction Data Service (CIDS) has been providing social science researchers and students in the UK with access to the ‘Origin-Destination Statistics’ collected by the statistical agencies (through decadal censuses).

• Origin-Destination Statistics, so-called because they involve two geographical areas, comprise:

- Special Migration Statistics (SMS): counts of migrants in the 12 months prior to each population census (in 2000-01,

1990-91 and 1980-81)

- Special Workplace Statistics (SWS): counts of those commuting to work at the time of the census (in 2001,

1991 and 1981)

• Sets of tables containing a number of variables or data counts

Tables and counts in the 2001 and Tables and counts in the 2001 and 1991 interaction data sets for the UK1991 interaction data sets for the UK

Data sets Level 1 Level 2 Level 3

2001 SMS 10 tables, 996 counts

5 tables, 96 counts 1 table, 12 counts

1991 SMS Set 2: 11 tables, 94 counts

Set 1: 2 tables, 12 counts

-

2001 SWS 7 tables, 936 counts

6 tables, 354 counts 1 table, 36 counts

2001 STS 7 tables, 1,176 counts

6 tables, 478 counts 1 table, 50 counts

1991 SWS* - Set C: 9 tables, 274 counts

-

* 10% sample

Data issuesData issues• Migration and commuting data sets are very important resource for research

and planning since there is no population registration system in the UK and there are no alternative sources that provide data of similar reliability or spatial coverage

• Large and complex data sets with which the user needs to gain some familiarity before using them with confidence

• Shortcomings include problems because of the requirement for the census agencies to preserve confidentiality and lower the risk of disclosure

• In 2001, the approach of ONS to reduce the risk of disclosure was a small cell adjustment method (SCAM), in which values of 1 and 2 were adjusted to either 0 or 3

• Another problem is that geographical boundaries change from year to year, thus obscuring the easy comparison of data over time

• The results of boundary change have prompted the CIDS team to produce

estimates of flows from the 1991 and 1981 censuses for 2001 geographical areas

WICIDWICID

• Software system used to access and extract data is called

Web-based Interface to

Census Interaction Data

• WICID programmed by Oliver Duke-Williams

• see Stillwell and Duke Williams (2003, 2005) for more details of the system

WICID WICID systemsystemarchitecturearchitecture

ResultsSQL

statements

Web browser

Web server

PHP

PostgreSQL

Session

state data

Interaction

data

Metadata

WEB

SERVER

USER

VIEW

DBMS

Server: Apache (http://www.apache.org)

Programming language: PHP: Hypertext Preprocessor (http://www.php.net).

DBMS:PostgreSQL (http://www.postgresql.org)

Add-on for spatial data:PostGIS (http://postgis.refractions.net/)

Building queries in WICIDBuilding queries in WICID • Major objective to create a user-friendly interface so that queries

can be constructed and data can be downloaded easily

• WICID has a guest function that allows anyone to logon and explore the system but those wishing to download data are required:

- to obtain an Athens userid and password- to become a registered census user

• The Census Registration Service facilitates access to the census

data resources (http://census.data-archive.ac.uk/)

• Currently the system is only available to members of the academic community in the United Kingdom

• Once registered, access to the CIDS homepage is at

http//cids.census.ac.uk/

CIDS home pageCIDS home page

WICID home pageWICID home page

Summary of commuting flows to and from Summary of commuting flows to and from

the City of London, 1991the City of London, 1991

Age pyramid of commuters from Havering to Age pyramid of commuters from Havering to

the City of London, 1991the City of London, 1991

General query interface before selectionGeneral query interface before selection

Map selection window

in WICID

Example Example of map of map selection selection of City of of City of London as London as destination destination

areaarea

Query to select commuting data to Query to select commuting data to City of London, 2001City of London, 2001

Screen indicating extraction completedScreen indicating extraction completed

Output and analysis in WICIDOutput and analysis in WICID

Output planning screenOutput planning screen

Analysis Analysis indicators indicators availableavailable

Mapping and analysis: ExampleMapping and analysis: Example• How have commuting flows to London boroughs changed between

1991 and 2001?

• Focus on the changes in flows within London and those arriving from the rest of England and Wales

• Aggregate statistics from the SWS for 1991 and 2001 suggest an overall increase of 20% in the commuting flows into London boroughs from 2.1 to 2.5 million persons per day

• Increase in flows from outside London is much smaller (8.6%) than the increase in inflows from other London boroughs (25%);

• Largest increase in commuting (nearly 60%) during the 1990s was taking place within boroughs

• Look at variations across London between boroughs

London boroughsLondon boroughs

Percentage shares of commuting Percentage shares of commuting inflows to London boroughs, 2001inflows to London boroughs, 2001

Inflows from elsewhere in London Inflows from outside London

Percentage changes in commuting inflows Percentage changes in commuting inflows to London boroughs, 1991-2001to London boroughs, 1991-2001

Inflows from elsewhere in London Inflows from outside London

ConclusionsConclusions• CIDS has now become established as one of a number of Data

Support Units serving social science researchers within the academic community in the UK

• In 2004, users in 169 academic institutions carried out 3,246 sessions using WICID

• However, use of the service increased significantly during the last quarter of 2004 and the first quarter of 2005 as the new 2001 interaction data sets have become available. We would expect the increase in usage to continue.

• Unfortunately the service is not available at the moment to academics or students outside the UK but it is hoped that this situation might be remedied in due course.

• An adapted version of the system (ACID) has been implemented that allows staff at the University of Queensland to have access to Australian internal migration data

Results from 2004 user surveyResults from 2004 user survey

Frequency % Valid % Cumulative

Very poor 4 2.4 2.4

Poor 1 .6 3.0

Average 46 27.9 30.9

Good 74 44.8 75.8

Very Good 40 24.2 100.0

Total 165 100.0

ConclusionsConclusions

• Various facilities in WICID have been developed to facilitate user access to the data before extraction and user analysis of data following extraction:

- Map selection toolMap selection tool constructed in response to feedback from users (particularly students) whose knowledge of the geographies of the UK is limited and who require help in selecting sets of zones

- Analysis facilitiesAnalysis facilities are useful because they add value to the raw counts extracted from the primary and derived data sets though currently only a restricted set of indicators is available

• Development of WICID over next 12 months will focus on map selection and analysis functions for 2001 data

ContactContact

My email: j.c.h.stillwell@leeds.ac.uk j.c.h.stillwell@leeds.ac.uk

AcknowledgementAcknowledgement

CIDS is funded by the ESRC/JISC under Census CIDS is funded by the ESRC/JISC under Census Programme Research Grant H507255177Programme Research Grant H507255177

http://cids.census.ac.uk