A detection is an observation
Frontex explains that its border-crossing figures count detections and that the same person may cross the external border more than once. The qualification matters even when a chart title uses the shorter word crossings. A count of recorded events is not automatically a count of distinct individuals.
This article uses that methodological note from a 2024 Frontex release. The release date remains 2024; reviewing the definition today does not turn its figures into current news. We are not publishing a new estimate of arrivals or residents here.
Follow an invented journey
Suppose one person is detected on two separate attempts at different locations. A system counting each detection can contain two events associated with that journey. A chart alone may not let the reader identify or remove that duplication. This fictional example illustrates the unit problem; it does not estimate the frequency of repeated attempts.
Now imagine a second person who enters under a lawful permission and later remains after it expires. A border-detection chart cannot be assumed to describe that later situation. Nor does a detected crossing, by itself, establish every subsequent decision about protection, residence or return.
Separate a flow from a stock
A flow describes events over a period. A population stock concerns people present at a point in time. To move between them, an analyst would need a defined starting population and evidence about entries, exits, status changes and measurement gaps. Adding annual detections is not a defensible shortcut to that stock.
This distinction also applies to geographical comparisons. A route is not necessarily a destination country, and a country where an event was recorded need not be a person's eventual place of residence. Keep the source's geography in the caption.
Annotate a chart before sharing it
Our proposed annotation takes four short lines. It makes the limits readable without hiding the pattern the chart actually shows.
- What is counted: use the source's unit, including the word detections where appropriate.
- Where and when: name the route or border coverage and the reference period.
- What can repeat or be missing: copy the relevant methodological qualification in your own words.
- What is not measured: do not relabel the chart as unique arrivals or the resident population.
Keep explanations separate from changes
A fall in detections is a statement about the recorded series. Explaining the fall requires additional evidence. Weather, surveillance, reporting and route changes are examples of questions to investigate, not causes established by this article. Apply the same discipline to an increase.
Use our Europe desk as a starting point, then open the linked primary source. Save its reference period separately from the date you read it. Source definition reviewed on 20 September 2026; no new live border total is claimed.