Mobile phone indicators and their relation to the socioeconomic organisation of cities

Thanks to the use of geolocated big data in computational social science research, the spatial and temporal heterogeneity of human activities are increasingly being revealed. Paired with smaller and more traditional data, this opens new ways of understanding how people act and move, and how these movements crystallise into the structural patterns observed by censuses. In this article we explore the convergence of mobile phone data with more classical socioeconomic data from census in French cities. We extract mobile phone indicators from six months worth of Call Detail Records (CDR) data, while census and administrative data are used to characterize the socioeconomic organisation of French cities. We address various definitions of cities and investigate how they impact the relation between mobile phone indicators, such as the number of calls or the entropy of visited cell towers, and measures of economic organisation based on census data, such as the level of deprivation, inequality and segregation. Our findings show that some mobile phone indicators relate significantly with different socioeconomic organisation of cities. However, we show that found relations are sensitive to the way cities are defined and delineated. In several cases, differing city definitions delineations can change the significance or even the signs of found correlations. In general, cities delineated in a restricted way (central cores only) exhibit traces of human activity which are less related to their socioeconomic organisation than cities delineated as metropolitan areas and dispersed urban regions.Comment: 19 pages, 9 figures, 2 table

Geographical veracity of indicators from mobile phone data : a study of call detail records data in France

PhD ThesisThe study of mobile phone data opens opportunities in many research domains and for many applications. One point of critique is that, within current analyses, mobile phone users are considered uniform and interchangeable. To counter this social atom problem, good research practice demands an increasing contextualization of research results, for example by confrontation with auxiliary datasets or geographical knowledge. The latter forms the starting point of this thesis. The main argument is that there exists a spatial knowledge gap when it comes to the use of indicators derived from mobile phone data. The presented studies assess the geographical veracity of indicators derived from Call Detail Record (CDR) data and the underlying methods used. Based on a CDR dataset of almost 18.5 million users in France captured during a 154-day period in 2007, they show how mobile phone indicators can be constructed for all individual users using big data technologies. Investigation then is on the performance, sensitivity to user choices, and error estimations of home detection methods, which form a primordial step for the aggregation of users in space. Next, a spatial analysis of the popular Mobility Entropy (ME) indicator is performed, revealing its bias to cell tower density, for which a correction is then proposed. Ultimately, the relations between mobile phone indicators, indicators from other data sources and city definitions in France are explored. The main contribution of the thesis is that it reveals multiple limits of the common practices, results, and interpretations that govern mobile phone data research. The presented studies challenge the veracity of mobile phone indicators in different, predominantly geographical, ways and open up discussion on what should be done to improve trustworthiness

An analytical framework to nowcast well-being using mobile phone data

An intriguing open question is whether measurements made on Big Data recording human activities can yield us high-fidelity proxies of socio-economic development and well-being. Can we monitor and predict the socio-economic development of a territory just by observing the behavior of its inhabitants through the lens of Big Data? In this paper, we design a data-driven analytical framework that uses mobility measures and social measures extracted from mobile phone data to estimate indicators for socio-economic development and well-being. We discover that the diversity of mobility, defined in terms of entropy of the individual users' trajectories, exhibits (i) significant correlation with two different socio-economic indicators and (ii) the highest importance in predictive models built to predict the socio-economic indicators. Our analytical framework opens an interesting perspective to study human behavior through the lens of Big Data by means of new statistical indicators that quantify and possibly "nowcast" the well-being and the socio-economic development of a territory

Aan welke doelstellingen moeten schooldoorlichtingen voldoen? Exploratieve studie in Vlaanderen met de Delphi Methode

De voorbije twee decennia zijn verschillende beschrijvende studies uitgevoerd naar de effecten van doorlichtingen. Vooralsnog is er echter in geen enkele onderwijscontext nagegaan welke verwachting verschillende  stakeholders stellen ten aanzien van de effecten van de doorlichting, en dus wat de doelstellingen zijn waaraan doorlichtingen zouden moeten voldoen. Deze wenselijke doelstellingen van doorlichtingen worden bepaald door de gedeelde verwachtingen van verschillende belanghebbenden in het onderwijsveld. Deze studie beoogt een inventarisatie van door de verschillende belanghebbenden in het Vlaamse onderwijs ondersteunde doelstellingen die aan een doorlichting zouden moeten worden gesteld. Deze inventarisatie biedt een referentiekader waaraan de effecten van een doorlichting kunnen worden afgetoetst. Omwille van het exploratieve karakter van deze studie op een afgelijnd domein waarbinnen nog maar weinig bekend is, werd gekozen voor de Delphi-methode. Door deze methode konden de standpunten van experten worden verkend en doorheen verschillende onderzoeksrondes met elkaar worden geconfronteerd. Algemene doelstellingen die ten aanzien van doorlichtingen worden gesteld, zijn de verantwoordingsgerichte, ontwikkelingsgerichte en de beleidsinformerende  doelstelling. Deze studie bevat ook een verdere concretisering van deze doelstellingen en een inschatting van het relatieve belang van elk van de concrete doelstellingen. Niet over elke doelstelling kon consensus worden bereikt. Onder meer de interpretatie van het grondwettelijke principe van  Vrijheid van Onderwijs en de invulling van de gescheiden rollen tussen inspectie en pedagogische begeleiding, liggen hieraan ten grondslag. In deze gevallen schept deze studie klaarheid in de argumenten die door verschillende experten worden gehanteerd.