Every year, tens of millions of people are displaced by natural disasters, and to date knowledge of their movement patterns has been sparse. The results of the study, now published in The Proceedings of the National Academy of Sciences (PNAS), could therefore help aid organisations to prepare and execute their relief efforts following a major disaster.
After the earthquake in Haiti, over 600,000 people left the capital Port-au-Prince, and over a million people were left homeless. With the help of mobile data provided by Digicel, the largest mobile operator in Haiti, the researchers looked for patterns in the movements of two million anonymous mobile users.
"When disaster strikes we tend to seek comfort in our nearest and dearest," says Xin Lu, who conducted the study together with colleagues Dr Linus Bengtsson and Dr Petter Holme. "We can see by the mobile data that where people were over Christmas and New Year, which was just before the earthquake, tended to be the place where they returned to afterwards."
The team also studied the everyday movements of people and found that although people moved greater distances after the earthquake compared to before, their daily movement patterns were extremely regular. Knowing a person's movements during the first three months after the earthquake, the researchers were able to show that it is possible to predict with 85 per cent probability the location of this person on a particular day in the ensuing period.
The researchers led the work on a paper last August where they, together with colleagues, showed how mobile data could be used to describe population movements after a disaster has happened. This present study takes the work a step further by showing the potential to predict population movements beforehand. Since the disaster, Linus Bengtsson and Xin Lu, both doctoral students at Karolinska Institutet's Division of Global Health, have initiated Flowminder.org, a non-profit organisation with the aim of disseminating analyses of population movements for free to relief agencies after disasters.
Xin Lu, Linus Bengtsson & Petter Holmen
Predictability of population displacement after the 2010 Haiti earthquake
PNAS, online first 18-22 June 2012