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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
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The Spatial Scale of Residential Segregation in Northern Ireland, 1991–2001 Chris Lloyd1, Ian Shuttleworth1 and David Martin2 1School of Geography, Archaeology and Palaeoecology, Queen’s University, Belfast, UK 2School of Geography, University of Southampton, UK 4th ICPG, The Chinese University of Hong Kong, 10-13 July 2007
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?
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
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
Northern Ireland Counties and major cities of Northern Ireland
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’)
Catholics as a percentage of NI population by community background: 2001 wards
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.
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
(R) (CB) Residential concentration profile for 2001: Catholics by religion (R) and community background (CB) for 1991 EDs, OAs, 1991 wards and 2001 wards.
(R) (CB) Residential concentration profile for 2001: Protestants by religion (R) and community background (CB) for 1991 EDs, OAs, 1991 wards and 2001 wards.
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.
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 1km2 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
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
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.
Spatial scale of residential segregation: 2001 E Cath: Isolation index for Catholics E Prot: Isolation index for Protestants Segregation indices against bandwidth for 2001 counts (by community background) over OAs, wards and 100m2 grid cells.
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
Ongoing work • Other approaches for exploring the spatial scale of residential segregation • Mapping of local segregation indices • Assessing degree to which results are generalisable
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.