1. WICID AND THE 2001 INTERACTION DATA John Stillwell and Oliver Duke-Williams School of Geography, University of Leeds Presentation at the Ninth International Conference on Computers in Urban Planning and Urban Management (CUPUM), University College London 14-15 July, 2005

2. Presentation What is WICID? What is WICID? Census 2001 interaction data sets Census 2001 interaction data sets Primary data sets Primary data sets Tables and counts compared with 1991 Tables and counts compared with 1991 Adjustment for disclosure control Adjustment for disclosure control WICID interface developments WICID interface developments WICID interface WICID interface Map selection tool Map selection tool Analytical functions Analytical functions Using the 2001 data: some examples Using the 2001 data: some examples Conclusions Conclusions

3. What is WICID? Web-based Interface for Census Interaction Data Web-based Interface for Census Interaction Data Software system developed as part of the Census Interaction Data Service (CIDS) Software system developed as part of the Census Interaction Data Service (CIDS) CIDS is funded by ESRC/JISC and is part of the Census Programme 2001-2006 CIDS is funded by ESRC/JISC and is part of the Census Programme 2001-2006 CIDS is a ‘Data Support Unit’ providing members of the academic community with online access to the census ‘Origin-Destination Statistics’ CIDS is a ‘Data Support Unit’ providing members of the academic community with online access to the census ‘Origin-Destination Statistics’ Overall aim is to encourage more use to be made of these data sets that are one of the products of the Census Overall aim is to encourage more use to be made of these data sets that are one of the products of the Census

4. Census 2001 interaction data sets Origin-Destination Statistics larger and more complex than from previous censuses Origin-Destination Statistics larger and more complex than from previous censuses Three sets of data in 2001: Three sets of data in 2001: Special Migration Statistics (SMS) for the UK Special Migration Statistics (SMS) for the UK Special Workplace Statistics (SWS) for the UK Special Workplace Statistics (SWS) for the UK Special Travel Statistics (STS) only for Scotland and include journeys to place of study as well as place of work Special Travel Statistics (STS) only for Scotland and include journeys to place of study as well as place of work

5. Geographical units used in 2001 SMS/SWS/STS Country Level 1 Level 2 Level 3 EnglandLondon Boroughs (33), Metropolitan Districts (36), Unitary Authorities (46), Other Local Authorities (239) CAS wards (7,969) Output areas (165,665) WalesUnitary Authorities (22)CAS wards ( 881)Output areas (9,769) ScotlandCouncil Areas (32)ST wards ( 1,176)Output areas (42,604) Northern Ireland Parliamentary Constituencies (18) CAS wards (582 )Output areas (5,022) TotalDistricts (426)Interaction wards (10,608) Output areas (223,060)

6. Data tables and counts compared with 1991 More tables but some dropped More tables but some dropped More counts but some dropped More counts but some dropped Counts include infants and students Counts include infants and students Counts for moving groups as well as wholly moving households Counts for moving groups as well as wholly moving households Classifications changed e.g. for ethnicity, economic activity, areas outside UK, ……. Classifications changed e.g. for ethnicity, economic activity, areas outside UK, …….

7. Tables and counts in the 2001 and 1991 interaction data sets Data sets Level 1 Level 2 Level 3 2001 SMS 10 tables, 996 counts 5 tables, 96 counts1 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 counts1 table, 36 counts 2001 STS 7 tables, 1,176 counts 6 tables, 478 counts1 table, 50 counts 1991 SWS* -Set C: 9 tables, 274 counts - * 10% sample

8. Tables and counts from 2001 SMS Level 1 and 1991 SMS Set 2 Variables 2001 Level 1 1991 Set 2 Tables Counts AgeTable 175Tables 1, 248 Family statusTable 254-- EthnicityTable 3 and 3N33Table 54 Limiting illnessTable 484Table 64 Economic activityTables 5 and 8378Table 7, 9, 1021 Moving groupsTable 616Table 22 TenureTable 732Table 8 and 8S7 OccupationTable 9288-- Some knowledge of Gaelic/Welsh/Irish Table 1036Table 11S and 11W 2 Marital status--Table 46

9. Adjustment for disclosure control Various methods used by ONS in 2001 Various methods used by ONS in 2001 minimum thresholds of people and households before the release of data minimum thresholds of people and households before the release of data record swapping between areas record swapping between areas small cell adjustment method (SCAM) small cell adjustment method (SCAM) SCAM assumed to adjust values of 1 and 2 to values of 0 and 3 SCAM assumed to adjust values of 1 and 2 to values of 0 and 3

10. Impact of SCAM on output area flows Only those with destinations in Scotland have been disclosure controlled Potential matrix of 223,060 origins by 180,456 destinations is > 40 billion cells ONS only provide data on OA to OA flows for cells 5, 6, 8, 9 11, 12 where flow is non-zero What are the counts included? MIG301 gives data on flows between output areas in the UK

11. Impact of SCAM: e.g. on distribution of interior cell values in SMS Table MG301 (excluding Scotland) Around 5 million migrations in total No values of 1 or 2 Over 1 million values of 3 Only cell values up to 30 shown Over 10 million values of 0 99.3% of values in cells are 0 or 3 accounting for 95% of flows

12. Other effects of SCAM This indicates ‘single table’ effect of SCAM This indicates ‘single table’ effect of SCAM There are also problems when comparing: There are also problems when comparing: (a) flows between tables (b) flows between spatial scales

13. Impact of SCAM when comparing tables: e.g. SMS at level 2 There are 2 tables at level 2 (wards) that contain total migrants MG201 Age by sex MG203 Ethnic group by sex These cells provide flows of total migrants between 10,608 wards in the UK and 9,432 wards in UK-Scotland (aggregations of flows in interior cells What differences occur in non-zero ward to ward flow totals?

14. Comparing total migrants in MG201 and MG203: distribution of absolute differences between alternative totals Over 1.1 million ward to ward flow totals Totals are different in 61% of cases Distribution of differences dominated by 3s Largest difference is 21 and frequency of larger differences is low

15. Impact of SCAM when comparing flows between spatial scales What are the effects of SCAM when comparing net migration rates based on data from: Table TT 37 SMS Table 104 and data aggregated up from: SMS Table 204 SMS Table 304

16. Net migration comparison for London boroughs Net migration rates per 1000 Borough TT 37 TT 37 SMS 104 SMS 104 SMS 204 SMS 204 SMS 304 SMS 304 Top five City of London4.875.0111.703.34 Kingston upon Thames3.333.952.763.14 Lambeth0.000.55-0.690.76 Sutton-0.151.390.661.30 Barking and Dagenham-0.49-0.16-0.23-0.16 Bottom five Brent-13.33-12.94-13.47-12.68 Kensington and Chelsea-13.50-13.70-14.49-14.37 Hounslow-14.04-13.12-14.24-13.49 Ealing-14.64-15.08-14.70-14.84 Newham-16.73-18.04-17.30-18.05 Mean net rate-7.10-6.94-7.34-7.18 Correlation with TT37 rate- 0.9850.9750.980

17. WICID interface developments CIDS homepage: http://cids.census.ac.uk/

18. WICID home page

19. WICID general query interface See paper in Evironment and Planning A (2003) for further details

20. Example of a query

21. Technical details WICID uses PostgreSQL (www.postgresql.org) as its DBMS and to provide support for the storage and manipulation of geometric features WICID uses PostgreSQL (www.postgresql.org) as its DBMS and to provide support for the storage and manipulation of geometric features A third party add-on to PostgreSQL called PostGIS (postgis.refractions.net) offers facilities to handle spatial data that follow the OpenGIS ‘Simple Features Specification for SQL’ standard A third party add-on to PostgreSQL called PostGIS (postgis.refractions.net) offers facilities to handle spatial data that follow the OpenGIS ‘Simple Features Specification for SQL’ standard In order for dynamic web pages to be created, a programming language is required and WICID uses PHP (PHP: Hypertext Preprocessor) (www.php.net) In order for dynamic web pages to be created, a programming language is required and WICID uses PHP (PHP: Hypertext Preprocessor) (www.php.net)www.php.net

22. What new facilities have been developed in WICID? Map selection tool Map selection tool This has been developed because of the demand by users (particularly students) to be able to view the geographical areas that they want to select This has been developed because of the demand by users (particularly students) to be able to view the geographical areas that they want to select Analysis tools Analysis tools This has been developed to provide users with the opportunity to generate some basic some statistical information and indicators derived from the data extracted This has been developed to provide users with the opportunity to generate some basic some statistical information and indicators derived from the data extracted

23. When choosing origins or destinations, users are confronted with a set of alternative selection tools

24. Map selection window in WICID WICID uses Post GIS extended PostgresSQL database and MapServer library components

25. Example: Selection of City of London as a destination

26. Analytical Tools Some basic statistics Suite of indicators Some of which require additional data: e.g. distances populations at risk Assembly of PARs is currently underway for 2001 data sets: needs specially commissioned counts for some variables

27. Example: Migration effectiveness by ethnic group for GO regions, 2000-01

28. Using the 2001 data: some examples Three examples based on data for London boroughs for 2000-01: Three examples based on data for London boroughs for 2000-01: Internal net migration and ethnicity Internal net migration and ethnicity Migration effectiveness by age Migration effectiveness by age Commuting connectivity Commuting connectivity

29. Example 1: Patterns of net migration for London boroughs in 2000-01 Rates of net migration with rest of GB Source: 2001 Census SMS level 1

30. The importance of disaggregating net migration for London boroughs, 2000-01 Net rates of migration for boroughs with the rest of GB Net rates of migration for boroughs within London Source: 2001 Census SMS level 1

31. Net migration (GL only), selected ethnic groups, 2000-01 Source: 2001 Census SMS level 1

32. Example 2: Migration flows and net balances by age group for London, 2000-01 Source: 2001 Census SMS level 1

33. Net migration effectiveness by age, London, 2000-01

34. Example 3: Connectivity within London Journey to work flows by destination borough, 2001 Source: 2001 Census SWS level 1

35. Out-migration and in-commuting connectivity for London boroughs by ethnic group, 2001 Source: 2001 Census SMS and SWS level 1

36. Conclusions CIDS and WICID now in successful operation since 2002 CIDS and WICID now in successful operation since 2002 2001 data sets accessible but work still underway on map selection and analysis tools to handle 2001 data 2001 data sets accessible but work still underway on map selection and analysis tools to handle 2001 data Users need take care when using 2001 data – SCAM means that there are several measures of the same count ! Users need take care when using 2001 data – SCAM means that there are several measures of the same count ! Examples demonstrate some of the insights that the interaction data sets can provide into behaviour Examples demonstrate some of the insights that the interaction data sets can provide into behaviour Comparisons between 1991 and 2001 possible but need to be aware of the definitional, measurement and geographical inconsistencies between the two sets of data Comparisons between 1991 and 2001 possible but need to be aware of the definitional, measurement and geographical inconsistencies between the two sets of data

37. Acknowledgement CIDS is funded by the ESRC/JISC under Census Programme Research Grant H507255177 http://cids.census.ac.uk