Information Technology Reference
In-Depth Information
so changes in the proportions of the elderly are reflected by changes in the
geography of the sexes.
More children will be born and brought up where there are more women.
Again one influences the other. We could struggle to see these influences on
three separate maps, one of the elderly, one of women and one of children. But
how much better is it to show these interrelated changes in a single image by
three-colour shading? Although more confusing initially, with a little study and
patience trivariate mapping reveals patterns that three separate maps cannot (you
cannot merge them in your mind). Now, though, rates of change rather than
proportions of people's movements and patterns of deaths and births are under
scrutiny. What aspects of change should be highlighted? (Box 5.3).
Aspects of the changes discussed above can themselves be examined more
closely. Change in the spatial distribution of children of different age groups
was examined, but produced an image considered not worth printing here. This
image, which presents such a jumbled picture, tells us that there has been little
uniform progression in these five-year age bands over time. The confusion is
caused by families moving; in many places only a minority remain in the same
block for ten years.
Box 5.3
Measuring the changes
Observed change (
O
) can be measured in many ways between two times
(T) and many places (
i
), for instance
O
i
=
T
i
2
−
T
i
1
T
i
1
T
2
−
T
1
(T
1
+
T
2
)/
2
or
Expected change can be calculated by
n
1
n
T
i
2
−
T
i
1
T
i
1
E
=
i
=
1
Then deviation from the expected is given by
D
i
=
E
−
O
i
E
Given six categories of housing and the national average prices (
P
)and
proportions (
) of these, it is possible to calculate from the local distribution
of average prices (
p
) an average house price (
h
) as either an arithmetic or
geometric mean:
W
i
=
6
(
W
i
p
i
P
i
1
P
6
W
i
p
i
P
i
ln
)
h
=
P
,
=
e
1
i
=
1
Search WWH ::
Custom Search