Measuring inbound tourism with mobile network operator data: The impact of international cross-roaming

The increasing availability of mobile network operator (MNO) data has opened up new opportunities for the production of official statistics, particularly in domains such as mobility and tourism. MNO data provide continuous, large-scale and fine-grained information that can complement, and in some cases partially replace, traditional survey and administrative data sources. However, their use also introduces new methodological challenges. This paper focuses on one of these challenges: the international cross-roaming and its impact on the measurement of inbound tourism indicators. Cross-roaming occurs when a foreign mobile device connects to multiple local MNOs within the same visited country during a single stay. This behavior can fragment the observation of tourists across different operators, potentially leading to an underestimation of the total number of overnight stays and, conversely, an overestimation of the tourist arrivals. Using data from multiple MNOs across several European countries within the framework of the Eurostat-funded Multi-MNO project, this study investigates the prevalence and magnitude of cross-roaming, its variability across origin and destination countries, and its impact on inbound tourism statistics. The results show that cross-roaming is widespread and can affect tourism indicators derived from data provided by a single MNO or from the naïve aggregation of data from multiple MNOs. To the best of our knowledge, this is the first study to provide an empirical assessment of the implication od cross-roaming for inbound tourism statistics. The analysis contributes to a more informed and careful re-use of MNO data for official statistics, particularly in the field of tourism statistics.