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we were fortunate that the total population, and its internal distribution, changed
little. Advantage can be taken of this fact. For instance, the underlying cartogram
that was used to portray the people of Britain did not, except in a few parts,
perceptibly change its shape.
Over long periods, which are examined later in this chapter, the underlying
population basemap changes with time. Over a much longer time period the
underlying base of geological maps change too as coastlines shift and mountains
rise. Just as over geological lengths of time usually a single landmass splits into
two, or two are joined, so too in human geography, when looking at change
over decades rather than millennia, most spatial units, of any size, will usually
correspond to just one or two predecessors. Occasionally the relationships will
be more complicated (Box 5.2).
Box 5.2
How closely connected?
The following tables show how often a one-to-one link was achieved and
how it is unnecessary to combine numerous districts when this approach
is taken.
Links between 1971 and 1981 Enumeration Districts
1971 EDs to each in 1981
1981 EDs to each in 1971
00
0 6
1
105 946
1
100 436
2
20 550
2
20 841
3
2347
3
3 085
4
287
4
582
5
49
5
163
6 0
6 3
74
7 4
85
8 8
90
9 2
10
1
10
9
11
2
11 - 18
17
Total 1981 EDs 129 211
Total 1971 EDs 125 476
Note
: 216 of the 1971 enumeration districts had identical grid references of
600 km East by 400 km North, a place in the North Sea, and could not be
linked to the 1981 set. These had been used to record the population off
shore for those districts with a coastline or inland water.
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