The database provides an inventory and a critical appraisal of data and estimates in the European Union and in selected member states. It contains estimates on the size of irregular migrant populations and indicators of their composition with regard to gender, age, nationality and sector of economic activity. The presentation is innovative in its consistent structuring and its carefully developed quality classification, which indicates whether estimates are more or less trustworthy. The summarizing tables are designed to give users the best possible overview of quantitative data in the countries, in a simplified form. The researchers involved in the creation of this database are aware that irregular migration is a complex issue. Therefore, quantitative information is accompanied by substantial background materials, both on issues of general concern and on the situation in individual countries.


Definitions of irregular migrants are problematic and complex, for reasons discussed in detail in the CLANDESTINO methodological report. For the sake of approximate comparability among countries, two broad types of irregularity have been distinguished in the database: irregular foreign residents (IFR) and irregular foreign workers (IFW).

  • IFR are foreign nationals without any legal resident status in the country they are residing in, and persons violating the terms of their status so that their stay may be terminated.
  • IFW are foreign nationals working in the shadow economy, including those with a regular residence status who work without registration to avoid due taxes and regulations.

The following graph shows the main overlaps and differences between the two groups, ignoring the fact that semi-compliance may blur some of the differences in reality

The more intensely coloured fields indicate the overlap between the two categories: adult foreign nationals who work in unregistered jobs, either without any residence status or on short-term, non-working visas (working tourists). They are likely to constitute the majority of all irregular residents in most EU countries.

In addition, IFR include foreign nationals without any residence status who do not work: children, aged and unemployed persons. Foreign nationals with falsified papers who are registered and seemingly legal for the authorities are usually not covered in estimates of IFR.

While the irregularity of the residence is the main criterion for IFR, the irregularity of work is decisive for IFW. Persons without legal residence status who are employed in regular, tax-paying jobs are usually not covered by estimates aiming at irregular work. On the other hand, IFW estimates include persons who are legally present in the country and perform irregular work. These are mainly three groups:

  • EU citizens who are working in the shadow economy.
  • Third country nationals with a right to stay who work in spite of having no right to work (e.g. asylum seekers).
  • Third country nationals who have a right to stay and work, but who are working in the shadow economy, avoiding due taxes and regulations.

Quality assessment


Stock tables

Template for presentation of stock estimates

Stock estimates refer to the total number of irregular foreign residents (IFR) or irregular foreign workers (IFW) in a country at a specific point of time. Each table consists of estimates of absolute numbers and of indicators for the composition with regard to gender, age, nationality, and sector of economic activity. All relative indicators are percentages of the groups in the total IFR or IFW population and thus should add up to 100%.

  • Total stocks: total stocks of irregular foreign residents or workers (for the whole country or specific cities or regions). 
  • Gender composition: absolute estimates, or estimated percentage of men and women.
  • Age composition: absolute estimates, or estimated percentage of age groups: 0-14 years (children); 15-60 (youth and persons in main working age);  60 and older (persons in or close to retirement age).
  • Nationality composition: absolute estimates individual nationalities, or estimated percentage of nationalities, sorted in order of quantitative relevance.

  • Economic sector composition: absolute estimates for individual sectors, or estimated percentage of sectors, sorted in order of quantitative relevance. Indicators differ strongly with regard to sector definition and specification. ‘Private household employment’ was summarized as one sector.

  • Other subgroups: open category for any estimate about groups of specific concern. It was suggested that these estimates could concern former asylum seekers, refugees or prostitutes, but any subgroup of irregular migrants for which an estimate exists could be added under this heading.


Definitions of irregular migrants are problematic and complex.  The database distinguishes between two broad types of irregularity, a simplification necessary in order to achieve some degree of comparability. Additions, like incl. EU (includes EU-citizens), 15 years plus (excludes children up to 14 years of age), IFR/working (excludes unemployed, children and aged persons without residence status), indicate important limitations of definitions.


The database summarizes estimates from 2000 to the present. Stock estimates are in principle estimates made at a specific point in time, usually the 31st of December of the year for demographic data. However, irregular migration estimates often do not indicate specific dates, only a year, if at all.
Note that the definition of EU-countries has changed in this time due to the accession of new member states. As EU citizens are rarely irregularly resident, this has a high impact on IFR numbers.


EU-member states


15 countries (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Netherlands, Portugal, Spain, Sweden, United Kingdom)


25 countries (15 countries + Cyprus, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, Slovenia)


27 countries (25 countries + Bulgaria, Rumania)



Estimates of irregular migrant populations may consist of one or more values which are sorted in the following way.


Estimate indicates that there are at least this many irregular migrants (also refered to as a conservative estimate). The lower value of a range estimate is also entered under minimum.


Estimate for which no indication of minimum or maximum estimate is feasible. The middle values of range estimates are also entered under central.


Estimate indicates that there are, at most, this many irregular migrants. Upper value of a range estimate is also entered under maximum.


The main type of data is indicated in the following way.

Data source

Short explanation

Enforcement data

Enforcement authorities reveal irregular migrants? status in the course of their work, usually against the migrants’ will (e.g. data from border guards, police, labour market inspection units).

Regularisation data

Irregular migrants may self-identify to authorities to become regular. Includes records of permanent regularization procedures and programmes.

Support service data

Irregular migrants may be identifiable in  some services (e.g. health services for uninsured persons). Support service data are based on records about such services.

Administrative data

All organisational statistics that cannot be summarized under the specific headings above (e.g. demographic data, school registers).

Census/ general survey

All surveys that are directed at general populations are included in this category. Census or population surveys often include a part of the irregular migrant population, although they are not always identifiable.

Expert survey

Expert surveys include the systematic collection and evaluation of estimates and indicators from institutional experts and/ or key informants in immigrant communities.

Migrant survey

All surveys in which irregular immigrants are directly targeted.

Employer survey

All surveys targeting employers and requesting information on the irregular employment of foreign nationals.

Economic data

Data on production, income, demand, etc.,  that is used for indirect estimations.

Multiple sources

Studies relying heavily on several of the above data sources.


Usually quotations of estimates, or expert opinions without explanation


Indicates the type of person or institution supplying the estimate and explains briefly the estimation procedure.


References are listed at the end of the table. They include references to CLANDESTINO country reports and the Classification Report, indicated as Working paper No.1 of the Database on Irregular Migration.


Population stocks at a specific point in time are influenced by population flows which are measured over a period of time, namely birth, death and migration over one year. Irregular migrant populations change also because people loose or gain a regular residence status.
Data about irregular migration flows are scarce, and indicators difficult to interpret. Therefore, it is even more important to be aware of the different types of inflows (movements into irregular status) and outflows (movements out of irregular status). Otherwise, there is the risk to overestimate the relevance of the most often used flow indicator which is border apprehensions.

First attempts to develop a simplified tabular overview of the available knowledge on inflows and outflows did not deliver satisfying results. For some countries, verbal summaries complemented by graphs are provided in the country profiles. The following categorisation used for the flow summaries is developed to raise awareness of the different types of flows:


As all populations do, irregular migrant populations change in size when people are born or die. Although there is hardly anything known about the size of these components, they should be kept in mind:

  • Births of irregular migrant children (inflows): European states do not recognize all children born on their territory as regular residents, so a baby may be born into irregularity. 
  • Deaths of irregular migrants (outflows): If irregular residents die, this is an outflow from this stock.


This type of flows concerns movement over a border of a country in violation of migration law:

  • Illegal entrance over a border (inflows): Illegal entries into an EU country occur when individuals cross an external border of the EU or enter from another EU country without the required travel documents. 
    Persons crossing an external border illegally either use regular ports of entry such as ports, roads and airports and seek entry with false documents or identities, or they may try to enter without inspection over land or sea.
    In the Schengen area, there are no ports of entry any more so that irregular migrants try to enter without inspection from one Schengen-state to another.
  • Exits of irregular migrants over border (outflows): Exits over the border of a nation state to another EU country or Non-EU country. They can occur in an unregistered fashion, when irregular migrants are not policed and remain undetected by public authorities. Exits can also be registered, for example when a person is deported or registered as crossing the border after an expulsion order.


This type of flows includes flows related to a migrant’s status change:

  • From regular status into irregularity (inflows): The most relevant inflow concerns persons who have entered the country with a tourist or other temporary visa and overstay the allowed period of residence (visa overstayers). Other persons have lived regularly in a country and stay after their status is withdrawn, for example after the rejection of an asylum application or the withdrawal of a temporary or permanent status after a serious criminal offence.
  • From irregularity to regular status (outflows): The most relevant outflow concerns persons who are individually regularized in cases of hardship or as asylum seekers, and persons profiting from a collective regularisation programme. Note that we consider any formal and documented suspension of deportation for a specific time as an outflow from irregularity, even if the state does not consider this specific status as a regular status.

Methodology: Link library


Duvell, F., Triandafyllidou, A., Vollmer, B. (2008): Report on ethical issues in irregular migration research, Report prepared for the CLANDESTINO project, October 2008

Duvell, F., Triandafyllidou, A., Vollmer, B. (2009): Policy brief on ethical issues in investigating irregular migration, Policy brief prepared for the CLANDESTINO project, November 2009 

Jandl, M., Vogel, D., Iglicka, K. (2008): Report on methodological issues, prepared for the CLANDESTINO project, November 2008

Vogel, D., Kovacheva, V. (2008): Classification report: Quality assessment of estimates on stocks of irregular migrants, Hamburg Institute of International Economics (HWWI), Database on Irregular Migration, Working paper No.1

Contribute to scientific debate

Particularly in a field with limited and dispersed knowledge, scientific communication may lead to improvements. Critical comments and suggestions for amendments and improvement are highly welcome. Currently, the database is only updated occassionally on a voluntary basis. However, if you have any comments or suggestions, do not hesitate to contact the database coordinators.

Proposed format for new estimates (Word document).

Send us your comments

Additional countries could be included in the database, provided that there is funding for country reports and database processing. Proposals are welcome.