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22
Two hundred and ninety-seven deaths of Acton residents
occurred outside the area and have been included in our returns.
The total number of deaths belonging to the district is therefore
727, which corresponds to a death-rate of 10.46 per 1,000 inhabitants.
This rate is what is called the crude death-rate and as such
is not comparable to the death-rate in the whole of England and
Wales, nor is it comparable to that of other districts, It has been
explained in previous reports that the death-rate of a district depends
among other things upon the age and sex incidence of its
population, and in order to establish a comparison these conditions
must be standardised. For this purpose the Registrar-General has
supplied each district with a comparability factor for adjusting the
local death-rate of 1931 and subsequent years. The comparability
factor for Acton before the change of boundaries on April 1st,
1934, was 107 and after April 1st, 108 In order to institute a
comparison with other districts the death-rate has to be multiplied
by the comparability factor. The standardised death-rate of Acton
would therefore be 11.29 per 1,000 inhabitants.
The following extracts from the Memorandum issued by the
Registrar General will explain how and why the comparability
factor is used.
The crude death-rate of an area should be multiplied by the
comparability factor in order to make it comparable, from a mortality
point of view, with the crude death-rate of the country as
a whole or with the mortality of any other local area, the crude deathrate
of which should be similarly modified with its own factor for
the purpose.
If the populations of all areas were similarly constituted as
regards the proportions of their sex and group conponents, their
crude death-rates (deaths per 1,000 population) could be accepted
as valid comparative measures of mortalities experienced by the
several populations.
In practice, however, populations are not thus similarly
constituted and their crude rates fail as true comparative mortality
indexes in that their variations are not due to mortality alone but
arise also from differences in their population constitution, the two
elements being combined in indistinguishable proportions. In
order to isolate the mortality factor it is first necessary to identify
and remove the population variable. For the present purpose,
the average mortality rates experienced in England and Wales during
the three years 1930-32 divided into 11 sex-age groups
have been adopted as the standard and have been applied to the
corresponding sex-age groups in the 1931 census population of every