1957 - United Nations Statistics Division

stances, be closely correlated with those for permanent
emigrants and immigrants as defined above, etc.
The Recommendations also set forth, in paragraph 19,
the following sub-categories of visitors, based on the
purpose of the visit:
(i) Visitors in transit
(ii) Visitors for holiday
(iii) Visitors for education
a. teachers under appointment by educational institutions
b. students attending regular sessions of educational
institutions
c. other visitors for educational purposes (e.g.
study tours, summer schools)
(iv) Visitors for business
(v) Other visitors
In paragraph 20 of the Recommendations, it is indicated
that a distinction between workers and non-workers
is desirable for frontier traffic.
These more detailed classifications are useful for various
users of the statistics; they do not generally concern
the basic information required in interpreting figures for
the more important categories of permanent emigrants or
immigrants, and need not be discussed here in further
detail.
Geographic and time coverage
The number of countries for which data are shown for
at least one year in anyone of Tables 27 to 31 is 72. It
would be desirable for several purposes that tables on international
migration should have an extensive geographic
coverage, but it is still more desirable that they
include sufficient data on the largest migratory movements
taking place in the world. From this point of view,
the coverage of Tables 27 to 31 is more satisfactory than
would appear from the mere consideration of number of
countries included.
The degree of completeness of the coverage varies between
continents. Among the more significant omissions
are Brazil and some other South and Central American
countries for recent years, and most African and Asian
countries or territories. In Europe, no statistics are available
for France, recent data on the characteristics of continental
migrants are lacking for Italy, and information
on continental movements is not available for the United
Kingdom.
While the collection of statistical information on travellers
and migrants is generally a continuous operation,
concomitant with the movements, important delays often
occur in the processing of the data. These delays account
for the gaps in the series for the year 1956 and even for
1955. In view of the importance of current data in the field
of migration, these gaps are regrettable and show the need
to accelerate the processing of data. At the other end of
the time period covered by the tables, that of the earliest
years, gaps actually indicate progress in several cases, some
countries having started only recently to compile the
statistics considered here.
In conformity with paragraph 27 of the Recommendations,
calendar-year series were preferred to those relating
to fiscal years or other twelve-month periods. The importance
of this type of variation on consistency and international
comparability of statistics of international
population movements has declined as a result of efforts
recently made by several countries to make calendar-year
tabulations available, sometimes in addition to the fiscalyear
data that may be required by legislation.
Accuracy of the data
Besides limitations resulting from methods of collection
and systems of definition, statistics of international population
movements and migration are also affected by errors
made at the time of collection and during processing. The
accuracy of migration statistics is also limited by two factors
not encountered in the case of other demographic
data. First, the definitions of permanent emigration and
immigration are based on intentions expressed by the
travellers, who may subsequently change their plans. Secondly,
it is known that clandestine movements occur across
certain frontiers. They escape statistical recording, except
perhaps in a very limited number of cases where provisions
are made for including the persons concerned in the
statistics, when their status is regularized.
The accuracy of statistics of permanent migrants cannot
be checked effectively by finding out how closely they fit
with the results of population censuses taken from time to
time in a given country and the balance of births and
deaths provided by the vital statistics system. This procedure
is, in most cases, useless because the magnitude of
migration in relation to natural increase and total size of
popUlation is so small as to fall within the margin of
absolute error of vital statistics and census data that are
fairly satisfactory on the basis of relative accuracy.
It remains possible to detect certain inaccuracies in migration
data through unexplained irregularities brought
out by comparison of figures for a series of years.
While travellers and migrants cannot be re-counted at
the point of their journey at which statistics were once collected
by a particular country, migrants are usually
counted by both the country of their last permanent residence
and the country of their intended permanent resirence.
This double count affords an obvious means for
evaluating the accuracy of migration data. Certain precautions
are, however, required when attempting a comparison
between the number of emigrants recorded by a
country E as leaving for a country I and the number of
immigrants recorded in country I as arriving from country
E. The coincidence of the two figures would require perfect
comparability. It is not surprising, therefore, that
corresponding figures from Tables 28 and 29 should differ,
In itself, this fact does not imply that the data lack in
reliability and comparability to the point of being of little
or no value. In order that corresponding emigration and
immigration figures should be even approximately equal
for any two countries, many difficult conditions would
have to be met. The principal ones are: equivalence in all
countries of methods of collection and definition of emigrant
and immigrant, and compatibility of the respective
lists of countries of intended permanent residence and of
countries of last permanent residence. Less fundamental
conditions would also have to be satisfied, such as recording
of persons changing their destination en route, of
births and deaths during the period of travel, and adjustment
of the data for differences in the time references of
the questions put to the migrants at the places where the
data are collected so as to deal with journeys extending
beyond the end of a particular calendar year. However,
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