Supplementary Information for Crowdsourcing the Robin Hood effect in cities

The dataset contains information about 14 million bank card transactions made by customers of the Banco Bilbao Vizcaya Argentaria (BBVA) in the metropolitan areas of Barcelona and Madrid in 2011. For both case studies, we only consider the credit card payments whose amount was inferior to 1000 euros, and which were made inside the metropolitan areas, by bank customers that lived and worked in the metropolitan area in 2011. Each transaction is characterized by its amount (in euro currency) and the time when the transaction has occurred. Each transaction is also linked to a customer and a business. Customers are identified with an anonymized customer ID, connected with sociodemographic characteristics (gender, age and occupation) and their postcode of residence. In the same way, businesses are identified through an anonymized business ID, a business category id, and the geographical coordinates of the credit card terminal. Since we are primarily interested in daily shopping mobility, we chose to consider the business categories that account for the top 90% of the daily shopping trips (see Figure S1). The proportions of shopping trips associated to each of the 20 business categories we selected are available in Table S1.