Yesterday Frontex released updated monthly data showing that 710,000 migrants crossed the EU’s external borders from January to September 2015. In a Twitter exchange with Nando Sigona (Univ. of Birmingham and Univ. of Oxford), Frontex clarified that it counts an individual migrant each time she crosses an external border; according to Frontex, “[t]his means that a large number of the [710,000] people who were counted when they arrived in Greece were again counted when [after passing through Greece, they entered] the EU for the second time through Hungary or Croatia.”
The 710,000 figure that was widely reported yesterday may overstate the number of individuals crossing the external borders by several hundred thousand. For example, Frontex reported that 350,000 migrants arrived in the Greek islands during the first nine months of 2015 and that 204,000 migrants crossed into Hungary during the same time period. Presumably a majority (or at least a very significant portion) of the migrants crossing into Hungary initially entered the EU via Greece and were counted at that time. Many of the tens of thousands of migrants who crossed into Croatia likewise presumably first entered the EU through Greece.
Frontex did add a disclaimer to its web site explaining the double counting: “Clarification: Frontex provides monthly data on the number of people detected at the external borders of the European Union. Irregular border crossings may be attempted by the same person several times in different locations at the external border. This means that a large number of the people who were counted when they arrived in Greece were again counted when entering the EU for the second time through Hungary or Croatia.”
And to be fair, Frontex has at times previously acknowledged that its figures include double counting. See the press statement from 14 September reporting 500,000 migrants having been detected at the external border: “However, a large number of the persons detected at the Hungarian border with Serbia had already been counted when they arrived in Greece from Turkey a few weeks earlier.” But the fact remains that much of the news coverage generated by the Frontex data will not explain the double counting.