We analyzed data from the locations of all Digicel mobile phones in Haiti before and after the earthquake. Our analyses cover the period 1 January to 11 March and include the movements of 2 million mobile phone SIM cards. We matched this data with census data and extrapolated the movement patterns to Haiti's population of 9.9 million persons.
Our results indicate that migration patterns of displaced persons are considerably different from what has previously been assumed, while the overall number of people displaced is similar to previous figures. Our estimates, projected from cell phone counts, suggest that on January 31st approximately 570,000 persons (22%) had left the Port-au-Prince metropolitan area. The three departments that received the largest absolute numbers of displaced persons were Sud, Ouest (the areas outside of the Port-au-Prince metropolitan area) and Artibonite.
The relative population increases in the departments outside Port-au-Prince were largest for Sud and Nippes (19 and 18% increases compared to pre-earthquake population levels), followed by Grande-Anse and Sud-Est (10% increase each). Since February the increasing population trend in the departments outside Port-au-Prince was reversed. On 11 March the population in the departments outside Port-au-Prince however still remained 3 to 12% above pre-earthquake levels.
After the initial large outflow, the population increased in Port-au-Prince from the end of January and during the rest of the analysis period. The population of Port-au-Prince is estimated to have been 15% smaller on 11 March than before the earthquake.
We estimate that the majority of people (68%) who moved into the Port-au-Prince metropolitan area during 1 February to 11 March lived in the Port-au-Prince area before the earthquake.