Money on the Move: Big Data of Bank Card Transactions as the New Proxy for Human Mobility Patterns and Regional Delineation. The Case of Residents and Foreign Visitors in Spain

Nowadays, more and more aspects of human activity include some sort of interaction with digital technologies. Those interactions result in the increasing production of data, which can be interpreted and explored as digital traces of human behavior. Discovery of patterns occurring in such data creates tremendous new opportunities in the fields of geography, urban planning, as well as other areas of social science, which are experiencing flourishing developments due to the availability of large-scale datasets reflecting human interactions, communications, and mobility. Many patterns in human behavior were discovered through mobile call records [1]–[5], social media posts [6]– [9], vehicle GPS traces [10], [11] or smart cards usage [12], [13]. For instance, it has been shown that community detection based on a country-wide network of cell phone communications creates spatially continuous and cohesive regions, similar in shape and number to the existing administrative divisions of the country [14]–[18]. This methodology was additionnally proven to be valid for human mobility networks extracted by means of call records [19], georeferenced tweets [9], and transportation systems data [10] (such as taxi GPS routes). In this paper, we explore a new type of data, giving insight on human economic activity: individual transactions performed via bank cards. This country-wide dataset, provided by the second largest Spanish bank BBVA, contains anonymized records of all bank card transactions executed by its customers (in any Spanish business) and of all transactions performed on BBVA card terminals, including by visitors from other countries. Unlike phone calls, this data does not allow to measure direct human-to-h