New ways to census a population

Portuguese people like to spend their holidays and weekends – if the weather allows it – on the beaches of the portuguese coast such as the Algarve.

Scientists have published a study in the Proceedings of the National Academy of Sciences showing the distribution of the Portuguese and French population.

(A) Location of Portugal and France in western Europe.

(B–E) Relative difference in predicted population density between the main holiday period (July and August) and the working period (September to June)

Empty areas are blue coloured, the red areas are – with a population growth of more than 60% – very crowded.

In Portugal these areas are mainly along the coast line and in the Algarve.

The close-up of Lisbon and surroundings shows that a lot of people move from the city to, for example, Costa da Caparica.

In France it looks the same: a big decrease of population during the summer – more than 30% in some areas – in the cities and a growth in places like Disneyland, Versailles or along the coastline.

(A) map of Portuguese population with data from the last census of population

(B) map of Portuguese population with data from mobile phone calls

(C) map of Portuguese population with data from satelite pictures

(D-F) close-up to metropolitan area of lisbon

The main aim of the scientists was to show that it is faster and cheaper to make population distribution maps by looking at the data of mobile phone calls.

That could also help in developing countries for example in Africa, where a lot of people are still not registered and the census data is expensive to obtain – because in these countries more then 70% of the population use mobile phones.

To show the precision of this method the scientist followed the mobile phone data in France and Portugal to make maps of the distribution of population.

“We chose Portugal because we have access to a data of phone calls and the existing Portuguese census data is really precise” said the scientist in an interview with the portuguese newspaper publico.pt.

Maps like this could quickly be provided in emergency or data-scarce situations.

Image 1: Study of Proceedings of the National Academy of Sciences

Image 2: Study of Proceedings of the National Academy of Sciences

Babette Jochum and Cristina Corrales Chicote

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