Towards a methodological framework for estimating present population density from mobile network operator data

The concept of present population is gaining increasing attention in official statistics. One possible approach to measure present population exploits data collected by Mobile Network Operators (MNO), from simple Call Detail Records (CDR) to more informative and complex signalling records. Such data, collected primarily for network operation processes, can be repurposed to infer patterns of human mobility. Two decades of research literature have produced several case studies, mostly focused on to CDR data, and a variety of ad-hoc methodologies tailored to specific datasets. Moving beyond the stage of explorative research, the regular production of official statistics across different MNO requires a more systematic approach to methodological development. Towards this aim, Eurostat and other members of the European Statistical System are working towards the definition of a general Reference Methodological Framework for processing MNO data for official statistics. In this contribution we report on the methodological aspects related to the estimation of present population density, for which we present a general and modular methodological structure that generalises previous proposals found in the academic literature. Along the way, we define a number of specific research problems requiring further attention by the research community. We stress the importance of comparing different methodological options at various points in the data workflow, e.g. in the geolocation of individual observations and in the inference method. Finally, we present illustrative results from a case-study based on real signalling data from a European operational network, complemented by numerical results from a simple simulation scenario. (C) 2020 Published by Elsevier B.V.