1. The Spatial Scale of Residential Segregation in Northern Ireland, 1991–2001 Chris Lloyd 1, Ian Shuttleworth 1 and David Martin 2 1 School of Geography, Archaeology and Palaeoecology, Queen’s University, Belfast, UK 2 School of Geography, University of Southampton, UK 4 th ICPG, The Chinese University of Hong Kong, 10-13 July 2007

2. Context Residential segregation in Northern Ireland an important issue - close links to territoriality and politics Meaning and reliability of results debated Problems: the modifiable areal unit problem and residential segregation What is the spatial scale of residential segregation?

3. Objectives To assess the degree of change in segregation indices with change in the zones used To explore the degree and nature of residential segregation in Northern Ireland

4. Structure Northern Ireland Community background and religion in Northern Ireland Methods Segregation indices and concentration profiles: 1991 and 2001 The Northern Ireland Census grid square resource Segregation indices and concentration profiles: grid square data for 2001 Summary

5. Counties and major cities of Northern Ireland Northern Ireland

6. Community background and religion Catholics as a percentage of NI population 1971 34% 1991 43% 2001 47% by religion 2001 45% by community background (‘religion or religion brought up in’)

7. Catholics as a percentage of NI population by community background: 2001 wards

8. Measures of segregation Concentration profiles: for example, the concentration profile for Protestants in Northern Ireland can be used to ascertain the proportion of Protestants who live in areas which have a population which is 75% or more Protestant.

9. Residential segregation: 1991

10. Zonal systems: 2001 Census counts Enumeration districts (EDs) Electoral wards for 1991 Output Areas (OAs) Electoral wards for 2001 2001 Counts transferred to 1991 EDs and wards by the NI Census Office, computer code developed by the project team run by Census Office staff and results returned to project team ZonesNMean sizeMean pop. EDs37293653159.0426.5 (91) OAs50222711913.6336 (01) Wards 199156624068250.52787.8 (91) Wards 200158223400735.22895.7 (01)

11. Residential segregation: 2001

12. (R) Residential concentration profile for 2001: Catholics by religion (R) and community background (CB) for 1991 EDs, OAs, 1991 wards and 2001 wards. (CB)

13. (R) Residential concentration profile for 2001: Protestants by religion (R) and community background (CB) for 1991 EDs, OAs, 1991 wards and 2001 wards. (CB)

14. Residential segregation: 2001

15. NI Census Grid square resource The grid-square data have been produced as a standard output from every NI Census since 1971. These data are unique; a similar dataset was generated from the 1971 GB Census but it was then discontinued. These data have been under used because they were stored in an inconvenient and hard- to-access COBOL database held by the NI Census Office.

16. NI Census Grid square resource The databases that were created give univariate population counts for a wide range of census variables for a regular lattice of 1km 2 grids throughout NI although only total population and household counts are given for cells which fall below a threshold of 25 individuals or 8 households. 1971, 1981, 1991: 1km square cells for all NI, 100m square cells for urban areas 2001: 1km and 100m square cells for all NI

17. Percentage Catholic in 1991

18. Percentage Catholic 2001

19. Residential segregation: 2001 Compares to, for example: D for OAs for religion: 0.692, for CB: 0.672 D for wards for religion: 0.617, for CB: 0.601

20. Residential segregation: 2001

21. Geographically weighted segregation indices Geographically-weighted variants of: –Index of dissimilarity –Index of isolation Feitosa, F. F., Câmara, G., Monteiro, A. M. V., Koschitzki, T., Silva, M. P. S. (2007) Global and local spatial indices of urban segregation. International Journal of Geographical Information Science, 21, 299–323.

22. Spatial scale of residential segregation: 2001 Segregation indices against bandwidth for 2001 counts (by community background) over OAs, wards and 100m 2 grid cells. E Cath: Isolation index for Catholics E Prot: Isolation index for Protestants

23. Conclusions There has been little change in residential segregation in NI between 1991 and 2001 Use of zonal systems with markedly different sizes has a large effect on segregation index results Altering the form of similarly sized zones has a limited effect Geographically weighted indices for different bandwidths allow assessment of the spatial scale of residential segregation

24. Ongoing work Other approaches for exploring the spatial scale of residential segregation Mapping of local segregation indices Assessing degree to which results are generalisable

25. Acknowledgements Richard Elliott and Robert Beatty of the Census Office (part of the Northern Ireland Statistics and Research Agency – NISRA) are thanked for making available the grid square data and the results for 2001 counts on 1991 zones. The support of the Economic and Social Research Council (ESRC) is acknowledged in funding, through awards RES-000-22-0271 and RES-000-23-0478, part of the work that made this research possible.