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75
the birth-rate of Hanover Square has again increased,
though it is not yet as high as it was in 1875, and that its
death rate has also slightly increased, but is still decidedly
lower than it was in 1875 or 1876; that with regard to
Mayfair the birth-rate has decidedly increased, being nearly
as high as it was in 1876, and the death-rate has slightly
increased; while in Belgravia the death-rate has increased,
although the bi. th-rate has slightly diminished.
From the figure in Table IVa., I have calculated, by
means of Dr. Bristowe's Formula,* the mean duration of
life, in the Parish and in each of the Sub-Districts during
1878, with the following results:—
Mean Duration of Life.
Hanover Square Sub-District 54.41 years
Mayfair ,, 58.92 ,,
Belgravia „ 40.87 „
Whole Parish 48.03 „
These are all rather less than in 1877, when the mean
duration of life in the whole Parish was 49.52 years.
The mean duration of life in London generally has also
decreased, for, whereas in 1877 it was 35.44 years, in 1878
it has only been 34.24 years; this fact being explained by
the increase in the death-rate, with an almost stationary
birth-rate.
The mean duration of life in this Parish, during the last
four years, has been as follows:—
In 1875 it was 46.67 years.
„ 1876 „ 47.96 „
„ 1877 „ 49.52 „
„ 1878 „ 48.03 „
So that in 1878 it has still been higher than in 1876, or
in 1875.
Of course in these calculations no allowance has been made
for movements of the population.
where x = mean duration of life
b = birth-rate of one unit of the population
d = death-rate „ „ ,,
and r = b — d = increase of unit in one year.