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25
From time to time questions are asked in Council which bear
upon the evaluation of the Infant Mortality over the short intervals
between successive Committee meetings; these intervals may be of
4, 5, or 6 weeks duration. ,
The calculation of the infant Mortality figure over short periods,
say a month, five weeks, or three months gives very fallacious
results.
It will be noted that in the definition of the infant mortality
figure, the births are counted for one year, and the deaths are of
children up to one year; the periods in both are the same—to wit,
one year.
In estimating the infant mortality say for four weeks, the births
cover a period of four weeks, but the infant deaths during that month
may be of children 6 weeks, 4 months or even 11 months of age.
Here it will be noticed that while the births cover 4 weeks, the
deaths may cover a duration of 51 or 52 weeks.
Two course are open, under the circumstances :—
(a) To count, in the case under review, only those deaths of
children up to 4 weeks of age, and estimate the infant mortality on
the births during 4 weeks, and the deaths of children up to 4 weeks
of age during the same period. It may and does happen that the
deaths of children up to 4 weeks of age may be absent or very few,
whereas the deaths of older children may be many. So that on this
basis, the current monthly infant mortality might be constantly
small and the annual infant mortality quite large.
The possibility of this discrepancy shows that this basis is
fallacious.
(b) To include all the births and all the infant deaths for a year
up to the end of the period being considered, and to give the infant
mortality figure for the twelve months thus brought in. This is the
method now adopted and gives fairly accurate results.