demographic yearbook annuaire demographique 1951

error in either direction may have an important effect on
the lx values for every age. The expectation of life at birth
(eo) will also be too high or too low.
The accuracy and the international comparability of life
table values are particularly suspect at the highest ages.
Those values depend, as has been said, on imperfect data
and frequently on somewhat arbitrary procedures. Certain
remarkable features-for example, the fact that the expectation
of life at ages over sixty is often distinctly higher in
countries where mortality in general is heavy than in
countries with low death rates-may thus merely reflect
imperfections of the tables.
Differences in the methods used for constructing life
tables (adjustment of data, graduation etc.) may affect the
reliability of the results and impair their international
comparability. The effect of such differences is, however,
probably much smaller than that of deficiencies in censuses
and death registration.
A full evaluation of the life table data presented in this
volume would require a detailed examination of the original
data and computations and a full knowledge of the conditions
of census enumeration and registration in each country.
Such a survey has not been possible; hence no indication
of reliability is given.
INTERNATIONAL MIGRATION
Statistics of international migration are presented in
tables 30 to 34. Table 30 presents overall statistics of international
travellers, classified by major categories of arrivals
or departures; tables 31 and 32 present data on emigrants
and immigrants, classified by countries of origin and destination;
tables 33 and 34 give statistics of emigrants and immigrants,
classified by age and sex.
The materials presented in the tables were, in most
cases, obtained from special communications sent by the
governments to the International Labour Office in reply
to a questionnaire. Supplementary data were extracted by
the United Nations Secretariat from official publications
of the countries concerned.
The problems involved in securing comprehensive and
comparable statistics of international population movements
are quite different from those that arise in connection with
other types of demographic data. One of the chief difficulties
is the absence of uniform and practical definitions of the
different types of population movements. For instance,
migrants must be distinguished from all other travellers
crossing international borders. Such a distinction is very
often difficult to establish in practice and in most cases
can only be made on the basis of declared intention regarding
length of stay, exercise of an occupation etc. As used
in the tables, the term "permanent emigrants" refers in
general to residents departing for a stay of a year or more;
"permanent immigrants" are non-residents arriving for a
year or more as well as residents so arriving after an absence
abroad of a year or longer. "Temporary immigrants" are
non-residents intending to exercise an occupation for a
limited period of time (usually less than a year) and their
dependents. In general, the line between "permanent" and
"temporary" or between "migrant" and "visitor" is drawn
at twelve months. Deviations from and modifications of
the above general concepts are explained in the footnotes;
so also are any other terms or concepts used. 13
13 For a fuller discussion of these difficulties, see United Nations
Problems of Migration Statistics ST/SOA/Series A. Population Studies,
No.5, Lake Success, New York, November 1949.
Data are required on movements of all peoples across
national frontiers if it is to be possible to combine statistics
of international population movements and of natural increase
to obtain a complete analysis of the changes observed
in the course of time in the size and structure of a given
population. An overall coordinated set of figures on international
movements of people departing and arriving, classified
by major categories of movement, presents also great
interest for the interpretation of the total figures corresponding
to anyone of the categories of movements, in particular
those for permanent and temporary emigrants and
immigrants. These data should, consequently, facilitate
comparisons between different countries and years. Data
of this type are presented in table 30 for 19 areas for the
years 1946-1950 and it is hoped that, in spite of their
limitations, they may prove useful in clarifying the nature
of the data on migration presented in the more detailed
tables that follow.
The nomenclature used in the table for major categories
of departures and arrivals is based upon that suggested
by the Population and Statistical Commissions in the Draft
Recommendations for the Improvement of International
Migration Statistics drawn up in 1949. 14 This nomenclature
was used by the International Labour Office in requesting
migration data from countries and is as follows:
I. Departures (except frontier traffic)
A. Total departures.
E. Permanent emigrants (i.e., residents departing
permanently) .
C. Temporary immigrants departing (departures of
persons who, on arrival, were classified in category
CC).
D. Residents departing temporarily.
£. Visitors departing (departures of persons who,
on arrival, were classified in category EE).
Special classes
(i.e., refugees, deportees etc.).
II. Arrivals (except frontier traffic)
AA. Total arrivals.
BE. Permanent immigrants.
CC. Temporary immigrants (i.e., non-residents intending
to exercise temporarily an occupation
and their dependents).
DD. Residents returning after temporary sojourn
abroad (arrivals of persons who, on departure,
were classified in category D).
EE. Visitors (in transit, on holiday, on business, for
education, for other purposes).
Special classes
(i.e., refugees, deportees etc.).
III. Frontier traffic
In compiling table 30 it was found that the description of
the categories used by some countries differ from the standard
definitions given above. In such cases the description
supplied by the countries are used. For this reason also the
reference letters are omitted in the table. Further, in order
to save space, the full designation of the categories is not
repeated in the table; similarly, where figures for only one
or two categories are available, the other categories are not
listed for that particular country. The definitions ofthe terms
"permanent" and "temporary" provided by the countries
14 See: Report of the Population Commission, Fourth Session, United
Nations document E/1313, 21 April 1949, Annex 3 (Mimeographed).
38