1971-1976 CD Comparability Indicator
A single digit numeric code which indicates whether or not the 1976 Census Collection District is comparable with a 1971 Census Collection District. Loss of comparability can be caused by a number of factors but the main ones are due to changes to CD boundaries to put them on suitable features; LGA changes; changes necessary because of urban growth; and changes necessary to provide population figures for new or modified statistical areas.
The code values used are:
0 = CD is perfectly comparable i.e. the CD has exactly the same boundary
1 = CD is comparable within a 10% dwelling limit i.e. a boundary change has occurred but no more than 10% by number of the 1971 dwellings in the CD have been added to or subtracted from the old CD in the boundary change
2 = CD is comparable except that a special dwelling (or dwellings) have been taken out and made a separate CD or CD's. In this instance the boundary must remain unchanged for the "outer" CD
3 = CD is not comparable due to a split of the 1971 CD into 2 parts (the old boundary being retained around the 2 new parts)
4 = As for 3 above except that the split has involved the creation of 3 or more parts
5 = CD is not comparable because of a split with no common boundaries being retuned
6 = CD is not comparable because it is an amalgamation of two 1971 CD's to give a 1976 CD (using the same outer boundary)
7 = CD is not comparable because it is an amalgamation of 3 or more 1971 CD's (using the same outer boundary)
8 = CD is not comparable because of an amalgamation without retention of any common boundaries
9 = CD is not comparable because of a complete re-allocation of boundaries (involving both splits and amalgamations)
(NOTE: Codes 5 and 8 are used instead of code 9 where the changes to the boundary of the 1971 CD have meant that not more than 10% by number of the 1971 dwellings in the CD have been added to or subtracted from the old CD in the boundary changes).