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.