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8
civilians, and under these circumstances the civilian population is
obviously the proper one to use for the calculation of death-rates.
An additional advantage in the use of National Register populations
is that these consist of habitual residents in each locality and not merely
of the persons who happened to be present therein on a certain date.
The deaths tabulated from the year 1911 onwards are also those of
habitual residents only, and therefore the use hitherto of populations
which in certain cases included very large institutional elements
chiefly composed of non-residents introduced in these cases serious
errors into the rates calculated from them, as pointed out in the
"Registrar-General's Annual Reports (See page 132, Report for 1913).
This source of error now of course disappears for the time being, and
in such districts an unavoidable break in the continuity of the previously
misleading rates will result. In any case however, the maintenance of
continuity is under present circumstances obviously impossible, and it
is felt that the present estimates will furnish death-rates calculated
to indicate as nearly as may be the health conditions of the civil
population.
The method by which the estimates of civil population have been
derived from the National Register returns may now be described.
The ratio of the total population less the males aged 15-65 years
to the number of females aged 15-65 years at the date of the census
was calculated for each administrative area, and this ratio was applied
to the number of the civil population of the district. A small adjustment
was necessary in order to make the sum of the estimates for the
several districts equal to the estimate for the country as a whole made
on the same basis. Further, the population in institutions was not
registered and this (taken to be the same in the aggregate for England
and Wales as at census date) together with a number of persons of no
fixed abode, were distributed evenly over the whole country. These
two adjustments raised the original estimates by about one per cent.
The question of the population to be used for the calculation of birthrates
has also required consideration. The births registered are not
only those of the children of civilians, and the estimates of civil population
therefore form an unsuitable basis for the calculation of birth-rates.
It is impossible to frame any estimate that would give reliable birthrates,
and it is suggested, therefore, that the birth-rates for 1915 be
based upon the existing estimates of total population for 1914. These
will sometimes be seriously in error owing to extensive migration
having occurred.