Problems 3: Inconsistency in geographical areas

• No migration data for Northern Ireland in 1990-01

• Local government re-organisation during the 1990s

• Hierarchy of zones constructed from the initial set of 459 districts in 1991 and 426 districts in 2001

• - ‘district’ geography (417 zones)

• - ‘intermediate’ geography (219 zones)

• - ‘100 zone’ geography (100 zones)

• - ‘city region’ geography (47 zones)

• - ‘Government Office Region’ geography (12 zones)