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12
We are now in a position to enquire how far the various rates
above given are reliable tests of the health and sanitary circumstances
of the district. The popular criterion is a comparison of the total
local rate with that of neighbouring districts, but such comparison
is open to error, unless the constitution of the population as regards
age and sex is taken into account.
Thus the death-rate of children under 5 years of age, and of
persons over 55 years is higher than the death-rate for all ages, whilst
the death-rate at ages 5—55 years is lower than the general rate ;
hence if in a population there is an excess of persons between these
latter ages the mortality would be very low when compared with a
more mixed population, or with one in which there was a
proportionately greater number of children under 5, and of persons
over 55.
We are thus in a position to see the influence of the birth-rate
upon the death-rate. The exceptionally high birth-rate for the past
year might reasonably be expected to have increased the death-rate,
since it causes an immediate increase in the population whose relative
mortality is highest, and this has, no doubt, been the case to a certain
extent.
On the other hand, the birth-rate in the district has been
unusually high for a considerable number of years past, and in this
way the population has come to possess an unusual proportion of
children from the age of 5 onwards, whose rate of mortality is now
low. Generally speaking, high birth-rates should cause lowered
death-rates and conversely low birth-rates a high death-rate. When
insanitary conditions are in evidence, a high birth-rate usually means
a high death-rate.
If thus we find one district or part of a district with a low birth-rate
and a low death-rate, or a high birth-rate or low death rate, whilst
another has a high birth-rate and a high death-rate, the conclusion
is that in the former the sanitary surroundings, occupations, or social
conditions are more favourable to life, than those of the latter.
In this connection, the Table at page 11 is of interest for the
comparison of the rates prevailing in the East and West Wards of the
district. The fact, that in your district there has been a sustained
high birth-rate and low death-rate for a number of years past, as
shown by the Table at Page 8 is a highly satisfactory circumstance,
indicating as it does, good sanitary conditions generally. The
sustained low rate of 12.2—12.3 for the past three years, is no doubt,
also to some extent, due to the immigration into the district during that
period of large numbers of young adults, whose death-rate is low.
I regret that accurate data are not available to work out the
death-rate at different age periods per 1,000 living at these ages; as
such a calculation affords the most valuable statistical evidence of
sanitary conditions.