Statistical annex introduction

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Most of the data published in this annex are taken from the individual contributions of national correspondents appointed by the OECD Secretariat with the approval of the authorities of Member countries. Consequently, these data have not necessarily been harmonised at international level. This network of correspondents, constituting the Continuous Reporting System on Migration (SOPEMI), covers most OECD Member countries as well as the Baltic States, Bulgaria and Romania. SOPEMI has no authority to impose changes in data collection procedures. It has an observatory role which, by its very nature, has to use existing statistics. However, it does play an active role in suggesting what it considers to be essential improvements in data collection and makes every effort to present consistent and well-documented statistics.

No data are presented on the native population, since the purpose of this annex is to describe the “immigrant” population as defined in the specific host country (i.e. the foreign or foreign born population, as the case may be). The information gathered concerns the flows and stocks of the total immigrant population and immigrant labour force, together with acquisition of nationality. The presentation of the tables in a relatively standard format should not lead users to think that the data have been fully standardised and are comparable at an international level, since few sources are specifically designed to record migration trends. Because of the great variety of sources used, different populations may be measured. In addition, the criteria for registering population and the conditions for granting residence permits, for example, vary across countries, which means that measurements may differ greatly even if a theoretically identical source is being used.

In addition to the problem of the comparability of statistics, there is the difficulty of the very partial coverage of illegal migrants. Part of this population can be counted through censuses. The number of immigrants who entered legally but then stay on after their residence permits (or visa) have expired can be calculated from permit statistics, but without it being possible to determine what the number of these immigrants that have left the country. Regularisation programmes, when they exist, make it possible to account for a far from negligible fraction of illegal immigrants after the fact. In terms of measurement, this makes it possible better to evaluate the volume of the foreign population at a given time, although it is not always possible to classify these immigrants by the year when they entered the country.

The rationale used to arrange the series has been to present first the tables covering the total population (series 1.1 to 1.6: inflows and outflows of foreign population, inflows of asylum seekers, stocks of foreign born and foreign population, acquisition of nationality), and then focus on the labour force (series 2.1 to 2.4): inflows of foreign workers, inflows of seasonal workers, stocks of foreign born and foreign labour force).

Since the nature of the sources used differs considerably across countries, each series is preceded by an explanatory note aimed at making it easier to understand and use the data produced. A summary table then follows (series A, giving the total for each host country), which introduces the tables by nationality or country of birth as the case may be (series B). At the end of each series, a table provides for each country the sources and notes of the data presented in the tables.

General comments on tables

a) The tables provide annual series for the ten most recent years (in general 1995-2004).

b) The series A tables are presented in alphabetical order by the name of the country in English. In the other tables, nationalities or countries are ranked by decreasing order of the stocks for the last year available.

c) In the tables by country of origin (series B) only the 15 main countries are shown and only when this information is available. “Other countries” is a residual calculated as the difference between the total foreign population and the sum of the nationalities indicated in the table. For some nationalities, data are not available for all years and this is reflected in the residual entry of “Other countries”. This must be borne in mind when interpreting changes in this category.

d) Tables on inflows of asylum seekers by nationality (series B.1.3) are presented for the top ten host countries in 2003. The data on outflows of foreign population (series 1.2), inflows of workers (series 2.1) and seasonal workers (series 2.2) are not broken down by nationality. Only totals are presented, in Tables A.1.2, A.2.1 and A.2.2, respectively.

e) The rounding of entries may cause totals to differ slightly from the sum of the component entries.

f) The symbols used in the tables are the following:

.. Data not available.

- Nil, or negligible.


OECD countries seldom have specific tools for measuring inflows and outflows of foreign population, and national estimates are generally based either on population registers or residence permit data. This note is aimed at describing more systematically what is measured by each of the sources used.

Flows derived from population registers

Population registers can usually produce inflow and outflow data for both nationals and foreigners. To register, foreigners may have to indicate possession of an appropriate residence and/or work permit valid for at least as long as minimum registration period. Emigrants are usually identified by a stated intention to leave the country, although the period of (intended) absence is not always specified.

When population registers are used, departures tend to be less well recorded than arrivals. Indeed, the emigrant who plans to return in the host country in the more or less long term can hesitate to inform about his departure to avoid losing the rights related to the affiliation to the register. Registration criteria vary considerably across countries (as the minimum duration of stay for individuals to be defined as immigrants ranges from three months to one year), which poses major problems of international comparison. For example, in some countries, register data cover a portion of temporary migrants, in some cases including asylum seekers when they live in private households (as opposed to reception centres or hostels for immigrants).

Flows derived from residence and/or work permits

Statistics on permits are generally based on the number of permits issued during a given period and depend on the types of permits used. The so-called “settlement countries” (Australia, Canada, New Zealand and the United States) consider as immigrants persons who have been issued “acceptances for settlement”. Statistics on temporary immigrants are also published in this annex for these countries since the legal duration of their residence is often similar to long-term migration (over a year). In the case of France, the permits covered are valid for at least one year (only students are not included). Data for Italy and Portugal include temporary migrants.

Another characteristic of permit data is that flows of nationals are not recorded. Some flows of foreigners may also not be recorded, either because the type of permit they hold is not used for statistics or because they are not required to have a permit (freedom of movement agreements). In addition, permit data do not necessarily reflect physical flows or actual lengths of stay since: i) permits may be issued overseas but individuals may decide not to use them, or delay their arrival; ii) permits may be issued to persons who have in fact been resident in the country for some time, the permit indicating a change of status, or a renewal of the same permit. The data for Australia do not include those who have been accepted for permanent settlement whilst resident in Australia, whereas data for Canada and the United States include all issues of permanent settlement permits.

Permit data may be influenced by the processing capacity of government agencies. In some instances a large backlog of applications may build up and therefore the true demand for permits may only emerge once backlogs are cleared.

Flows estimated from specific surveys

Ireland provides estimates based on the results of Quarterly National Household Surveys and other sources such as permit data and asylum applications. These estimates are revised periodically on the basis of census data. Data for the United Kingdom are based on a survey of passengers entering or exiting the country by plane, train or boat (International Passenger Survey). One of the aims of this survey is to estimate the number and characteristics of migrants. The survey is based on a random sample of approximately one out of every 500 passengers. The figures were revised significantly following the latest census in each of these two countries, which seems to indicate that these estimates do not constitute an “ideal” source either. Australia and New Zealand also conduct passenger surveys which enable them to establish the length of stay on the basis of migrants’ stated intentions when they enter or exit the country.


The statistics on asylum seekers published in this annex are based on data provided by the United Nations High Commission for Refugees. Since 1950, the UNHCR, which has a mission of conducting and co ordinating international initiatives on behalf of refugees, has regularly produced complete statistics on refugees and asylum seekers in OECD countries and other countries of the world (

These statistics are most often derived from administrative sources, but there are differences depending on the nature of the data provided. In some countries, asylum seekers are registered when the application is accepted. Consequently, they are shown in the statistics at that time rather than at the date when they arrived in the country (it should be pointed out that acceptance of the application means that the administrative authorities are going to review the applicants’ files and grant them certain rights during this review procedure). In other countries, the data do not include the applicants’ family members, who are admitted under different provisions (France), while other countries register the entire family (Switzerland).

The figures presented in the summary table (Table A.1.3) generally concern initial applications (primary processing stage) and sometimes differ significantly from the totals presented in Tables B.1.3, which give data by country of origin. This is because the data that the UNHCR receives by country of origin combine initial applications and appeals, and it is sometimes difficult to separate these two categories retrospectively. The reference for total asylum applications remains the figures shown in summary table A.1.3. The data by nationality for the United States refer to the number of applications registered rather than the total number of persons concerned. For further details by host country, refer to Chapter VI of the 2003 statistical yearbook of the UNHCR.


Two questions must be asked before examining stocks of immigrants in OECD countries: 1) Who is considered as an “immigrant” in OECD countries (the answer is clearest for inflows), and 2) What is the nature of the problems of international comparison?

Who is an immigrant?

There are major differences in how immigrants are defined. Some countries have traditionally focused on producing data on foreign residents (European countries, Japan and Korea) whilst others refer to the foreign-born (settlement countries, i.e. Australia, Canada, New Zealand and the United States). This difference in focus relates in part to the nature and history of immigration systems and legislation on citizenship and naturalisation.

The foreign-born population can be viewed as representing first-generation migrants, and may consist of both foreign and national citizens. The size and composition of the foreign-born population is influenced by the history of migration flows and mortality amongst the foreign-born. For example, where inflows have been declining over time, the stock of the foreign-born will tend to age and represent an increasingly established community.

The concept of foreign population may also include immigrants having retained the nationality of their country of origin as of the second and third generations born in the host country. The characteristics of the population of foreign nationals depend on a number of factors: the history of migration flows, natural increase in the foreign population and naturalisations. It is possible to find people having always the statute of immigrant even if they born in the host country. The nature of legislation on citizenship and the incentives foreigners have to naturalise both play a role in determining the extent to which this occurs in practice.

Sources and problems of measuring the immigrant population

Four types of sources are used: population registers, residence permits, labour force surveys and censuses. In countries that have a population register and in those that use residence permit data effectively, stocks and flows of immigrants are most often calculated using the same source. There are exceptions, however, as some countries instead use census or labour force survey data to evaluate the stock of the immigrant population. The same problems for studying stocks and flows are encountered whether registers or permit data are used (in particular, the risk of underestimation when minors are registered on the permit of one of the parents or if the migrants are not required to have permits because of a free movement agreement). To this must be added the difficulty of “clearing” series regularly to eliminate permits that have expired.

Census data enable comprehensive, albeit infrequent analysis of the stock of immigrants (censuses are generally conducted every five to ten years). In addition, many labour force surveys now include questions about nationality and place of birth, thus providing a source of annual stock data. However, some care has to be taken with detailed breakdowns of the immigrant population from survey data as sample sizes can be very small. Inevitably, both census and survey data may underestimate the number of immigrants, especially where they tend not to be registered for census purposes, or where they do not live in private households (labour force surveys generally do not cover those living in institutions such as reception centres and hostels for immigrants). Both these sources can detect a portion of the illegal population, which is by definition excluded from population registers and residence permit systems.


Naturalisations must be taken into account in the analysis of the population of foreigners and nationals. Also, differing national approaches to naturalisation between countries must be considered when making international comparisons. In France and Belgium, for example, where foreigners can fairly easily acquire nationality, increases in the foreign population through immigration and births can eventually contribute to a significant rise in the native population. However, in countries where naturalisation is more difficult, increases in immigration and births amongst foreigners manifest themselves almost exclusively as rises in the foreign population. In addition, changes in rules regarding naturalisation can have significant numerical effects. For example, during the 1980s, a number of OECD countries made naturalisation easier and this resulted in noticeable falls in the foreign population (and rises in the population of nationals).

However, host-country legislation is not the only factor affecting naturalisation. For example, where naturalisation involves forfeiting citizenship of the country of origin, there may be incentives to remain as a foreign citizen. Where the difference between remaining a foreign citizen or becoming a national is marginal, naturalisation may largely be influenced by the time and effort required to make the application, and the symbolic and political value individuals attach to being citizens of one country or another.

Data on naturalisations are usually readily available from administrative sources. As with other administrative data, resource constraints in processing applications may result in a backlog of unprocessed applications which are not reflected in the figures. The statistics generally cover all means of acquiring the nationality of a country. These include standard naturalisation procedures subject to criteria such as age or residency, etc. as well as situations where nationality is acquired through a declaration or by option (following marriage, adoption or other situations related to residency or descent), recovery of former nationality and other special means of acquiring the nationality of the country).


Inflows of foreign workers

Most of the statistics published herein are based on the number of work permits issued during the year. As was the case for overall immigration flows, the settlement countries (Australia, Canada, New Zealand and the United States) consider as immigrant workers persons who have received a permanent immigration permit for employment purposes. In each of these four countries, it is also possible to work on a temporary basis under various programmes (these data are also available in this annex). Data by country of origin are not published in this annex.

The data on European countries are based on initial work permits granted, which sometimes include temporary and seasonal workers. Major flows of workers are not covered, either because the type of permit that they hold is not covered in these statistics, or because they do not need permits in order to work (free circulation agreements, beneficiaries of family reunification, refugees). Some data also include renewals of permits. The administrative backlog in the processing of work permit applications is sometimes large (as in the United States, for example) and affects the flows observed, The data may also cover initial entries into the labour market and include young foreigners born in the country who are entering the labour market.


The international comparison of “immigrant” workers faces the difficulties already mentioned earlier regarding measuring the overall stock of immigrants and taking into account different concepts of employment and unemployment.

For the European countries, the main difficulty consists of covering EU nationals, who have free labour market access in EU Member States. They are sometimes issued work permits, but this information is not always as readily available as for third-country nationals. Switzerland recently revised the sampling of its labour-force survey in order to compensate for the information that was no longer available on EU workers in registers of foreign nationals following the signature of free movement agreements with the European Union. These bilateral agreements enable employees who are holders of “EU/EFTA” permits to change their job or profession (professional mobility), and this change is not registered in the Central Register for Foreign Nationals, the usual source for statistics on the stock of foreign workers.

The use of work permit statistics can result in counting the same person more than once if the data include temporary workers and this person has successively been granted two permits during the same reference period. On the other hand, holders of “permanent” residence permits allowing access to the labour market are not systematically covered, especially since it is not always possible to determine the proportion of those who are actually working.

Another difficulty concerns determining the number of unemployed, self-employed and cross border workers. The unemployed are generally included, except when the source is work permit records and when permits are granted subject to a definite job offer. Self-employed and cross-border workers are much less well covered by statistics. The reference periods of data are highly variable, as they are generally the end of December for register data, and the end of the first quarter of the reference year for employment survey data.

The management of population registers (when the population in the labour force can be identified) and work permits results in numerous breaks in series when expired work permits are eliminated, when this is not done automatically, or when regularisation programmes are implemented, which often give priority to foreigners who can show that they are employed or have a job offer. When these breaks occur, the analysis of the growth of the stock of foreign workers is significantly biased.

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