1976-1981 CD Comparability indicator

A single digit numeric code which indicates whether or not the 1981 Census CD is comparable with a 1976 Census CD. Loss of comparability can be caused by a number of factors but the main ones are due to LGA changes; changes to CD boundaries 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 where population and dwellings are not affected even though there has
    been a change in boundary of CD.
2 = CD is comparable within a 10 per cent dwelling limit i.e. a boundary change
    has occurred but no more than 10 per cent by number of 1976 dwellings in the CD
    have been added to or subtracted from the old CD in the boundary change.
3 = 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 old boundary is
    retained around the new parts.
4 = CD is not comparable due to a split of the 1976 CD into two parts (the old
    boundary being retained around the two new parts).
5 = As for 4 above except that the split has involved the creation of three or
    more parts.
6 = CD is not comparable because of a split with no common boundaries being
    retained.
7 = CD is not comparable because it is an amalgamation of two 1976 CD's to give
    a 1981 CD (using the same outer boundary).
8 = CD is not comparable because it is an amalgamation of three or more 1976
    CD's (using the same outer boundary).