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10
Note on the
London Life
Tables, with
Short Life
Tables
prepared by
Mr. B. E.
Spear.
London Life Tables.
The first extended life-table for London is contained in the Annual Report of
the Medical Officer for 1901 (Appendix 1), and relates to the period 1891-1900.
The second for the period 1901 to 1910, will be found in the Annual Report for 1912
(vol. III., p. 105). In the ordinary course of things a similar table would have been
prepared for the period 1911-1920, but owing to the war the results would not have
been comparable with the earlier tables and there are practical difficulties in the
construction of the table for this period owing to the absence of necessary data for
the war years. Under the circumstances, it was decided to construct short lifetables
showing the probability of living through periods of five or ten years of life,
and to carry the tables back to the earliest years of death registration, for the purpose
of comparison. The latest pre-war table is for the years 1911-1912, while the years
taken to represent the post-war experience were 1920 to 1922.
The first short life-table constructed for London is contained in the fifth annual
report of the Registrar-General and relates to the year 1841. Life-tables based upon
only one year's records are not satisfactory owing to the wide range of fluctuation
in mortality, especially in the earlier years of last century. The life-table for 1841
gives the expectation of life as 37 years. In the same report life-tables are shown
for Liverpool and for Surrey, and in these areas the expectation of life was 26 and
45 years, respectively. Of 100,000 born half would have died in the metropolis
before attaining the fortieth year, while in Liverpool half would have died before
the tenth year on the basis of the mortality in 1841. There was at that time three
years' difference between the expectation of males and females in London, the
male expectation being 35 and the female 38 years.
For the purpose of comparison it may be mentioned that Halley's life-table,
based upon the mortality of Breslau in Silesia, in the years 1687 to 1691, gave an
expectation of 33.5 years ; while the Carlisle life-table for England nearly a century
later gave a figure of 38.7 years.
In a supplement to the 75th annual report of the Registrar-General short lifetables
are given for the counties and principal county boroughs of England and
Wales based on the mortality in the years 1911 and 1912. The method of calculation
used in constructing the tables was devised by Dr. E. C. Snow and is fully described
in the report referred to. This method has been adopted for calculating the series
of short life-tables for London for successive periods between 1840 and 1922. In
the case of the earlier periods it was not possible to adopt Dr. Snow's method entirely,
but he has been followed as far as practicable in order to retain comparativity with
other tables constructed by his method.
One difficulty met with is worthy of mention, namely, that until 1875 the registration
of births was not compulsory, and thus an unknown but perhaps relatively
small number of births was not recorded. In order to avoid error from this source
the probability of living during the first five years of life was derived direct from the
mortality at ages 0 to 5 on the basis of the relationship found to exist during decennia
subsequent to the introduction of compulsory registration. It was further found
that the probability of living during successive five-year periods between the ages
10 and 25 was more accurately obtained from the mortality rates of the five-year
age-groups than from Dr. Snow's tables. For the age-group 5 to 10 in the earlier
decennia the figures of the English life-table No. 3 (1838 to 1854) contained in the
28th annual report of the Registrar-General (p. lxxiv.) were taken as the basis for
the necessary formulae.
The mortality-rates at ages and by sexes which have been used for the construction
of the nine life-tables for London are shown in the subjoined table:—