Irregular migration: Major differences across Europe

The numbers of irregular migrants and the political measures taken vary greatly between European countries. This is shown by the recently completed EU Horizon project “Measuring Irregular Migration” (MIrreM), coordinated by Albert Kraler, migration researcher at the University for Continuing Education Krems. In this interview, he explains how many people are living in Europe without regular status, what strategies countries are pursuing, and what impact this has on society and the economy.

Interview by Roman Tronner

Dr. Kraler, the topic of irregular migration is polarizing and is often associated with illegal border crossings. How does research define irregular migration?

First, it is important to distinguish between irregular mobility – i.e., crossing one or more borders without the necessary requirements such as visas or valid identity documents – and the prolonged stay of migrants without a right of residence. Irregular border crossing does not mean that migrants will later be without a right of residence. Since there are hardly any legal routes of entry for refugees, many are forced to take irregular routes, for example. A study shows that between 2009 and 2021, more than 55 percent of irregular migrants apprehended at the EU's external borders were later recognized as refugees.

Irregular migrants are people without the right to reside in the country in which they live. The reasons for this are restrictive immigration and residence laws that do not sufficiently take into account the realities of life and make it difficult or even impossible to enter the country legally or obtain a residence permit. In addition, many people in an irregular situation previously had residence permits that were linked to employment, study, family, or international protection and which they lost for various reasons. Others entered the country legally on tourist visas or under visa-free arrangements. Children can also be “born into” irregularity if their parents do not have the right to reside in the country.

Many factors can lead to irregularity: in addition to irregular immigration, which receives the most attention in media reports and is often associated with images and reports of shipwrecks, dramatic rescue operations, and controversies over the reception of rescued persons, regulatory deficits are often a decisive factor.

At the EU level, only third-country nationals without a residence right are considered part of the irregularly residing population. In practice, however, EU citizens can also lose their right of residence under free movement rules – for instance, if they have not yet resided long enough in another EU member state and lack sufficient means of subsistence, or due to criminal convictions. Another relevant category consists of migrants with a temporary residence status. This includes, for example, asylum seekers whose right to remain is still being decided, as well as persons without a residence right who have been ordered to leave the country but whose removal has been temporarily suspended. The suspension of an obligation to leave does not mean that a right of residence exists. In Germany and Austria, this legal status has its own term, Duldung, although the concept differs significantly between the two countries.

The MIRREM project set out to obtain more reliable figures on the extent of irregular migration in Europe. Did the project achieve this goal, and how did you go about it?

Yes, but the estimates are based on very different methods – and mostly on indirect methods, i.e., methods that are not based on direct surveys in which respondents provide information about their residence status. The diversity of estimation methods naturally makes comparison difficult. Of the 20 countries examined in detail by MIrreM, five have no estimates at all. The MIrreM research project has compiled the various existing estimates from 13 European countries as well as the United States and Canada, assessed their quality, and obtained a clearer picture of the extent of irregular migration. In addition, in a separate sub-project, it has developed new estimation methods, one of which is based on social media use and provides estimates for numerous countries worldwide. This method is currently being further developed in cooperation with Eurostat.

So how many irregular migrants are there currently in Europe?

According to estimates, irregular migrants account for less than 1 percent of the total population in these European countries. As part of the project, we have developed an interactive map that shows the figures for each European country. The latest available figures can be viewed with a single click. In Austria, the number of “irregular migrants” is regularly estimated for the purposes of population statistics. For the year 2022, this estimate shows 62,000 irregular migrants as the average value. That is 0.7 percent of the total population. However, it is important to note that this figure also includes unreported EU citizens. If this group is excluded, the number of irregular migrants according to this estimate is around 43,600, a figure that is also supported by an estimation method based on social media developed as part of the project. Our research also shows that since 2008, the number of irregular migrants and their share of the population has increased in three countries: Austria, Germany, and Spain. In five countries, the estimated number of irregular migrants has remained the same: Belgium, France, Italy, the United Kingdom, and the United States. The numbers have declined in Finland, Greece, Ireland, the Netherlands, and Poland. Overall, there has been no clear change in the number and proportion of the irregular migrant population in Europe since 2008 – contrary to the public portrayal of a continuous increase in irregular migration.

The research project also looked at policy measures for dealing with irregular migration. What are the arguments in favor of regularization measures such as those implemented in Spain or Ireland?

They make people's stay legal and therefore traceable for the authorities. This facilitates integration and reduces social risks (such as possible exploitation by employers). The labor market also benefits because the labor potential becomes visible and controllable. Politicians often fear that regularization could act as a pull factor. However, research shows that migration is primarily determined by economic conditions and social networks – not by the availability of regularization measures.

What forms of regularization are there?

We understand regularization as an official, state-defined process that grants persons without residence rights temporary or long-term legal status. There is a wide variety of differently structured regularization measures in Europe: on the one hand, there are temporary programs, and on the other, there are long-term mechanisms. We have summarized the further results of our research in our Handbook on Regularization Policies.

Based on your research, what form of regularization do you recommend to states?

Depending on the situation, both forms can be effective: Temporary regularization programs can respond to specific situations. The German Opportunity Residence Act introduced in 2022 (applications can be submitted until the end of 2025) provides for a temporary residence permit of 18 months for persons who have had a temporary suspension of deportation for at least five years (i.e., whose deportation order has been temporarily suspended) and who meet certain integration requirements, such as employment and language acquisition.

“Regularization mechanisms” create permanent ways out of irregularity. The permanent “arraigo” mechanism in Spain (first introduced in 2004 and subsequently expanded) offers several alternative options for regularization based on social, employment-related, family, or education-related criteria.

Migration policy is largely within the remit of EU member states. This is probably a major reason for the lack of uniformity. Does the EU have no means whatsoever of exerting influence in terms of regularization?

Although the EU has no direct jurisdiction over national immigration laws, its institutions nevertheless influence national decisions through coordination, legal frameworks, and political discourse.

A key piece of legislation is the 2008 Return Directive – a proposal for a return regulation is currently under negotiation. It allows Member States to issue residence permits ( Art. 6 para. 4).

Judgments of the Court of Justice of the European Union (CJEU) or the European Court of Human Rights (ECHR) are also important. All EU member states, as well as the European Union itself, are parties to the European Convention on Human Rights (ECHR) and are therefore bound by the rulings of the ECtHR. In the past, rulings by both courts have obliged states to grant residence rights or refrain from deportation in certain cases on the basis of human rights rules and EU law

What insights were gained from the project on the return of migrants without residence permits to their countries of origin?

The return of irregular migrants was not the focus of the project. However, we did address the issue in connection with questions of right of residence and in connection with statistics and estimates on irregular migration. For example, the claim that only 20 percent of return decisions are implemented is widespread in political discourse at the EU and national levels. However, calculating the return rate as the ratio between return decisions and confirmed returns in a given year is extremely flawed and potentially misleading. For example, one and the same person may have several return decisions in the same country. Similarly, return decisions in different countries concerning the same persons are counted separately, for example, if a person who has received a return decision in Austria goes to Germany and receives another return decision there. Basically, it is the same procedure, but it is counted twice. Another aspect is that there is no systematic EU-wide recording of how many forced returns are carried out after a “return decision” (obligation to leave) has been issued.

My guess is that the implementation rate is greatly underestimated – but ultimately, we don't know.

An interesting finding in this regard: Enforcement of return and regularization are often seen as opposing options. In reality, however, these two paths out of irregularity take place at different points in time. A recent study[i] shows that the probability of ending an irregular stay by returning is highest within the first two years after the obligation to leave takes effect. After this period, the probability of voluntary departure remains virtually unchanged, increasing only minimally and leaving regularization as the only viable way out of irregularity.

How did you make the results accessible to the general public and policymakers?

In addition to the interactive map on irregular migration mentioned above, we have produced short videos for YouTube. And for policymakers and experts, we have published the results in the form of handbooks, including the aforementioned handbook on regularization policies and a handbook on data on irregular migration, which presents important concepts and methodological issues using practical examples.

What is the key finding from the research project for you?

Regularization has proven to be an effective means of granting people regular residence status in a controlled manner and on the basis of specific criteria. It is clear that concrete design and long-term monitoring are essential in this process; excessive bureaucratic requirements or criteria that are difficult to meet can lead to the goal being missed. Politicians must recognize that formal eligibility does not automatically lead to effective measures – simplified procedures and a balance between case-by-case discretionary decisions and clear eligibility rules are the way forward. Policymakers can learn from different regional practices, such as the human rights-based approach in Latin America or the integration-related approaches in Europe, in order to develop flexible yet coherent frameworks.

About the project:

The research project “Measuring Irregular Migration” (MIrreM), funded by the EU's Horizon program, investigated the extent and characteristics of irregular migration in a total of 20 countries in Europe, North Africa, and North America from 2022 to September 2025, as well as innovative methods and policy responses to irregularity, including the regularization of irregular migrants. The project consortium comprised a total of 18 partners and was coordinated by the Department of Migration and Globalisation at the University for Continuing Education Krems.

[i] https://www.bamf.de/SharedDocs/Anlagen/DE/Forschung/Kurzanalysen/kurzanalyse1-2023-mimap.html?nn=282388