Problems of changing definition and availability - 1

• Confusion because of nomenclature: Set 1 (ward) and Set 2 (district) in 1991 but level 1 (district) and level 2 (ward) in 2001

• Family status and occupation tables for district migration data in 1991 but not in 2001, whereas marital status table in 1991 discontinued in 2001

• New categorizations of variables used in 2001 e.g. ethnic groups at district scale (but only white/non-white in NI)

• Occupation table based on the new National Statistics Socioeconomic Classification (NS-SeC) that replaced the classification of social class based on socio-economic group (SEG) used in 1991