Studying national and international migration flows with Twitter data

Human migration is the movement of people from one place to another with the intentions of settling, permanently or temporarily, in a new location. It is for sure an activity that have strongly characterized human history. There are many reasons to move: natural disasters, diseases, economic crisis, discrimination, learning stays, all lead to the need of going to live in a different place. In taking the decision about the destination, the cost and the risk of the journey must be considered. The distance, cost of living and traveling are all parameters to deal with. The information on migration has been traditionally collected by census surveys. In the last few years, the advent of social networks gave researchers the possibility to gather big amount of geolocated data about people and their movements in a cheaper and quicker-to-update way. From this arise the possibility to study migrations at a new level of detail. The purpose of this thesis is twofold: first, I aim at exploring the usefulness of social network data/micro-blogging to monitor migrations within Europe. This includes the validation of the migration flows obtained online versus census data. As it is shown, the online data can provide a valuable view on the flows not captured by the census/registration offices. Secondly, known models for characterizing mobility flows (Gravity and Intervening Opportunities) are tested on the obtained migration network. This test is carried out with migrations in all Europe and Turkey. Results show that the model that better describes the migration flows is the radiation model. This is due to the fact that when people migrate, possible jobs opportunities are more important than distances.