demographic yearbook annuaire demographique 1951

available for 1930) and in 5 cases the percentage change
was reckoned to the year 1948 or 1949 (later data not
being available).
These data indicate that among countries that had crude
rates of 15 or more per 1,000 in 1930, almost half showed
decreases of over 40 per cent and most of the remainder
showed decreases of 20 to 39 per cent.
The areas included in the table are even less representative
of the world situation than those included in table C.
However, they have a wide enough spread, from the geographic
and ethnic points of view, to indicate that significant
progress has been made during the past two decades in the
reduction of mortality. Relative decreases among the areas
of high mortality in 1930 are large enough to transcend the
considerations of change in age composition discussed above
and leave no doubt that a genuine decrease has occurred.
Even among the areas for which the statistics are ofdoubtful
accuracy or are acknowledged to be deficient, the changes
indicated have some significance. Presumably coverage of
these populations has improved over the period under consideration.
If so, such decreases as the statistics show may
actually understate the absolute decline in the crude rate,
though the relative decline may in some cases be overstated.
Among the 72 areas for which data are available at both the
beginning and the end of the period (including the 44 areas
treated in table D) 14 reported declines of 40 per cent or
more; 34 reported declines of 30 per cent or more. Most of
these are areas with initial rates approaching or surpassing
20 per 1,000.
As mentioned earlier, the African population is scarcely
touched in this analysis. Two examples of recent findings
may therefore be cited. In the sample census of the African
population of Southern Rhodesia, data on births and deaths
for the year ending 31 August 1948 were collected. These
data yield an estimated crude death rate of 18.1 per 1,000. 1
Preliminary results of a recent study among the tribal Arabs
of Libya indicate a crude death rate of about 40 per 1,000.
These two observations do not give an adequate basis for
generalization. They serve, rather, to underline the need for
further information.
Sufficient data for a more detailed consideration of general
mortality trends in each major region of the world are
contained in the tables of this Yearbook, but restrictions of
time and space have made it necessary to confine the present
TABLE D
Distribution of 44 areas by the level of the crude death rate
in 1930 and the percentage decrease 1930-1950
Number oj areaS by percentage
decrease 1930-1950
Crude rate All Under 20 20-39 40per cent
in 1930 areas per cent per cent or over
All classes. . . . . . . . . .. 44 21 15 8
Under 10.0......... 7 16 1
10.0-14.9 ........... 18 213 4 1
15.0-19.9........... 11 1 8 2
20.0-24.9........... 5 1 1 3
25.0 or over......... 3 1 2
1 Including 3 cases in which the rate increased.
2 Including 1 case in which the rate increased.
1 See "Sample Census of the Indigenous African Population,"
Economic and Statistical Bulletins oj Southern Rhodesia, Vol. XVII, No.8,
Central African Statistical Office, Salisbury, 21 July 1949. Pages 7-12.
treatment to broad comparisons between 1930-1932 and
1948-1950 for the world as a whole. Interesting variations
during the intervening period and among different parts of
the world may be found in the data here presented. They
raise some problems of analysis and interpretation, but they
are not likely to invalidate the general import of the findings
reported above.
An important aspect of these findings is their implications
with respect to population growth. Many of the areas which
have reported significant declines in the death rate show
little or no change in the birth rate. With birth rates
approaching 40 per 1,000 and death rates dropping to the
neighborhood of 10 to 15 per 1,000, annual rates of natural
increase will range between 2.5 and 3 per cent. The official
statistics indicate such rates in an increasing number of
countries. At the rate of 2.5 per cent per year, a population
will double in 28 years. While the conquest of mortality
makes a striking contribution to human welfare, the prospect
of such rapid population growth calls for some concern if
that welfare is to be protected and enhanced.
MORTALITY BY AGE AND SEX
The scope of an analysis of trends in mortality specific for
age and sex is necessarily more limited than that of an
analysis of crude death rates. Data on deaths classified by
characteristics of the decedent and corresponding statistics
of the population on which to base rates are not so widely
available as are the data required for the computation of
crude rates. Nevertheless, it is only on the basis of such
detailed information that differences and changes in mortality
can be truly measured or well understood. Furthermore,
a great deal can be inferred, from the information
that is available, concerning areas for which statistics do
not yet exist.
As concerns infant mortality rates, which are based on
the number of live births and therefore do not require
statistics of the population classified by age, the requisite
data are more extensively available than is the case for other
age groups. Hence it is convenient to consider infant mortality
separately, then mortality at the later ages.
. Infant mortality. The infant mortality rate (here defined as
the number of deaths under 1 year of age per 1,000 live
births, both items referring to the same year) is widely used
as an indication of the general health and well-being of a
population. Because of the vulnerability of the human infant
to the ravages of disease, malnutrition, poor medical care
etc., this rate reflects rather faithfully the living conditions
of the general population. It responds quickly and perceptibly
to improved conditions. Rapid declines in the crude
death rate are often attributable mainly to a reduction in
infant mortality.
In interpreting the infant mortality rates presented in
table 19, the usual caution as to the reliability of the basic
figures on infant deaths and live births should always be
kept in mind. The completeness of registration of live births
and of infant deaths varies from country to country, and
within the same country the coverage and tl;1e accuracy of
data collected are not necessarily the same for both these
items. Distortions of the rates are therefore to be expected
in all countries or areas in which the basic statistical data
are not completely and accurately recorded. If, for example,
births are completely registered while some infant deaths
escape registration, the resulting rate understates the actual
mortality. Overstatement occurs if infant deaths are prop-
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