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Ariel, indeed, the Registrar-General calculates that their
pretence would have raised the mortuary-rate from 19.9 to
20.4. All this is no doubt true. And it is important; for
it shews (what I have always maintained) that mere differences
in the death-rate are of themselves of little value in
determining the relative healthiness of different years or of
different localities; and that it is always necessary in such
investigations to take into consideration the meaning of the
actual facts from which, and the method by which, the statistical
results are obtained.
I may mention, further, in relation to the above subject,
that some years ago I was induced to make a mathematical
investigation of the mutual relations of the birthrate
and death-rate, and I showed, conclusively, that any
given death-rate had a very different meaning according as
the population in which it occurred had a high birth-rate
or a low birth-rate. Thus (other things being equal), while
an annual death-rate of 20 in 1,000, maintained over a
series of years, in a population with a birth-rate of 20 in
1,000 similarly maintained, implies an average duration of
life of 50 years, the same death-rate, associated under
similar conditions with a birth-rate of 50 in the 1,000,
implies an average duration of life of only 31 years. I
need scarcely add that the general death-rate indicates
healthiness or imhealthiness only in its relation to the
average duration of life; and that the remarks I have just
made tend in some degree to diminish the force ot the
Registrar-General's remarks in reference to the effect on
the death-rate of a paucity of young children.
There is no doubt, however, that the year 1986 has
been an exceptionally healthy year. For, as the Registrar