Relative to other demographic phenomena, like births and deaths, migration is assuming increasing importance in measurements of population change. Unlike other demographic phenomena, however, migration flows pose particular challenges to the production and measurement of reliable and widely comparable statistics.
Reasons for these challenges can be found both in the characteristics of migration itself and in current strategies for collecting and interpreting migration data. Migration flows, for example, fluctuate rapidly while many demographic patterns change only slowly. International migration is also the only demographic statistic that is currently produced simultaneously by two different national statistical institutes — one in the country of departure and one in the country of arrival. Despite the difficulties, reliable international migration data are urgently needed in the areas of population projections and policies.
UN recommendations on international migration statistics provide a useful target for improving the collection, reliability and comparability of such statistics in Europe. This article explores the current state of European migration statistics and the prospects for greater coordination.
Factors in the Current Unreliability of Migration Statistics
The fluctuation and unreliability of international migration statistics are exacerbated by the use of inappropriate sources of data. Except for specific migration surveys, data sources are not generally put in place with the ultimate aim of counting migrants. As a result, statistical collection of migration data is a by-product of administrative data collection systems. Moreover, countries often do not have the same political, economic, or social interest in collecting data on immigration and emigration. Finally, confusion between "migration" and "migrant" and between migratory "flows" and "stocks" does not improve data collection of migrant flows and stocks.
Data unreliability also stems from policy decisions in the countries involved in a given migration flow. The closure of frontiers and the rise of illegal migration and asylum seekers make the calculation of migration flows more difficult and require differentiation between a country's de facto and de jure populations. It is impossible to estimate precisely the number of illegal immigrants. Beyond this, these estimates cannot be included in administrative data collection that measures legal immigration.
At the same time, the increase in the number asylum claims makes the comparison and estimation of flows difficult. Many countries do not consider asylum seekers as migrants when they compile their statistics (for example, Belgium, Netherlands and Germany). In these cases, while claims are pending, asylum seekers are counted as temporary migrants waiting for a long-term stay permit.
In Europe, an increase in migration within the countries of the EU and a decrease in changes to usual countries of residence have made these measurements even more complex. First, it is now easier for EU citizens to live in another European country without asking for a permit to stay. In fact, the reliability of migration statistics concerning European citizens is lower than that for non-EU citizens. Secondly, intra-European migration is often no longer considered as relevant by administrations in charge of migration management. The focus is now often on immigrants from outside the European Union, asylum seekers, and illegal migration. In certain cases, migration statistics are no longer even compiled for European citizens.
The European Model
The Eurostat measurement of flows between Denmark and Germany in 1998 illustrate the difficulty of measuring migration flows. When the registered level of immigration in Germany is compared with the Danish equivalent, it appears that Denmark underestimates immigration flows by 50 percent. In fact, the definitions used in Germany and in Denmark are very different: Germany considers every entry an "immigration" after seven days, while Denmark requires an intended duration of three months. Therefore, very short-term migrations are included in Germany but not in Denmark. This example makes clear that among the challenges of improving the comparability of international migration statistics, harmonizing the concepts and definitions of migration are no less important than resolving the problems of poor reliability of data collection systems.
How is it possible to explain such large differences between statistical figures supposed to measure the same migration flow? First, the national definition of migration often differs from the internationally recommended definition. In addition, the reliability of migration data is sometimes so poor that, even when countries define migration in the same terms, the resulting figures may differ widely. Lastly, unless all sub-populations are identified, it is not certain that the data cover entirely the populations in question. (For example, asylum seekers, students, seasonal workers and even EU citizens are important types of sub-populations that are often not included in migration statistics in Europe.) In sum, the development of comparable migration systems requires both the implementation of reliable data collection systems and the coordination of ideas about and definitions of migration.
Improving Current Systems of Migration Data Collection
In this context, Eurostat, the United Nations Economic Commission for Europe (UN/ECE), and other international bodies are working to improve the overall reliability and comparability of the migration data collection. One means of resolving the difficulties of migration measurement is to look to the UN-recommended definitions of long- and short-term migration as a standard upon which to base measurements. This would do much to improve the reliability and comparability of statistics.
There remain, nevertheless, a number of unique challenges that must be overcome if migration statistics are to be truly reliable. According to the UN Recommendations on Statistics of International Migration (revised in 1998), long-term international immigration is recorded after an individual enters a country and establishes his usual place of residence there for one year or more. UN definitions of short-term immigration state that the period of residence is limited to between three months and one year.
Several types of sources are currently used to collect migration data, which are more or less useful to meet the UN recommendations:
Before these data sources can be considered appropriate for the implementation of UN recommendations, however, they must meet several other criteria. Importantly, the data must be reliable and consistent, and the whole population must be covered by the data source, including all sub-populations and all types of migrants. If data collection systems are modified, or if new systems are introduced, there are other factors that must be considered including: the feasibility and cost of the change or introduction; any national rules regarding administrative and statistical systems; and, the national sensibilities regarding migration.
Given these caveats, the census is the least satisfactory option because it only counts new immigrants from the time that the census was taken. Also, long and short-term migrations are not differentiated.
Cross-border counting would theoretically allow for the counting of entries and exits. In this context, UN recommendations could be followed by asking a question at the entry and another at the exit about the expected or real length of stay or by stamping passports to make length of stay apparent. However, these systems are generally unreliable. Not all migrants need a visa (none of the EU citizens traveling within Europe, for example). Moreover, the fact of obtaining a visa or work permit does not mean that the person will use it nor stay until its expiration, which would indicate the duration of the stay.
Other data sources are simply problematic to implement. Updating residence or work permit files, for example, is difficult and specific migration surveys are limited by the sample size.
Population Registers in Brief
Population registers, however, record both immigration and emigration, link the entry and exit dates of an individual and clearly record the actual length of stay. Generally speaking, there have also been improvements in population register quality in Western Europe. In Spain, for example, revisions that were made every five years are now permanent. Countries like Belgium and the Nordic states have centralized their registers and have improved links between their diverse administrative files including the population register (as well as social security, property records, employment records, and activity records concerning firms' activities, i.e. the number of employees, types of production, and financial results). This avoids double counting and improves data verification. As computerization has grown, so has the amount of information produced because the capacity for variables and tables has increased and definitions have been refined. It is only through centralization, however, that population registers are reliable, yet even this does not guarantee international compatibility between immigration and emigration figures.
To remedy this, a removal card system would require a person leaving country A to take a form upon departure that would be given to authorities in country B upon arrival. Later, country B would determine whether it was a long- or short-term migration and inform country A of the determination. This would ensure compatibility between immigration and emigration statistics. The advantages of this process are demonstrated by its successful use in the Nordic countries.
Europe Aims for Greater Comparability, Reliability
As discussed earlier, comparability of international statistics is frequently so low that it hinders correct statistical analysis. In conjunction with overall improvement of data collection, two analytical approaches have been developed to promote comparable and reliable migration data. The first method consists of bilateral co-operations between pairs of country in order to examine the details of differences between data. Eurostat has used this method to link data between Belgium, on one side, and Denmark, Sweden and Italy, on the other side. This research is pioneering insofar as it is the first time that individual data has been linked between two data files produced by two completely different systems in two different countries. Therefore it allows comparison of individual data rather than comparison of aggregate data.
The second method uses a basic mathematical model to correct estimations of intra-European migration. However, this method is not a substitute for coordinating the criteria and collection processes between European countries.
In addition, many countries have made concrete efforts to improve the reliability and comparability of their own national statistics. Governments have sought to improve reliability through a variety of measures:
For a few countries, the gap between the national definition and the international recommended one is relatively small and therefore greater harmonization may be more easily achieved. But in a large number of countries, the data sources and national practices are so different from the internationally recommended definition that harmonization is practically impossible. The objective, therefore, may only be minimal comparability rather than complete harmonization.
UN Recommendations as a Realistic Goal
While there is a growing consciousness of the impact of diverse national definitions, the UN criteria have not been formally adopted anywhere. The Nordic countries, which come the closest in this regard, have systems in place for exchanging migration information, and therefore provide an important example of creating reliable international migration data. They demonstrate that collaboration, either bilateral or within a multinational framework, can produce reliable and comparable data, but its first goal must be to standardize the fundamental concepts and criteria, the collection methods, and the variables and data collected.
The 1998 UN recommendations represent a common goal for improving international migration statistics. Ideally, all the countries with a system of population registers and active records of changes in the place of residence could, at least in the long term, exchange minimum information on international migrants. The inclusion on all national forms of a common body of questions for declaring a change of residence would further this goal. In addition, data exchange between statistical services or qualified administrations could prove very useful.
Real harmonization, however, will occur only with the development of real political will. Until recently, national interests have taken precedence over the need for internationally comparable statistics. Moreover, the lack of reliability is a significant problem at a national scale. Increasingly, however, international confrontations are bringing to light the significance of data comparability and reliability. In Europe, only focused political energy at a European level will lead to a substantial improvement in the estimation of migration currents. Most importantly, the ultimate objective should not be to record a maximum number of migrants but rather to measure migration in a way that is as near as possible to the UN definition.
Michel Poulain can be contacted at email@example.com with any questions.
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