Déterminants des migrations de l’Afrique vers l’Europe : du court séjour à la migration durable et / ou irrégulière

International migration is often seen as a single, one-way movement from a country of origin to a host country. In contrast to this unidirectional view of migration, this thesis focuses on the articulation between temporary and long-term migration in the context of migration between Africa and Europe. More specifically, it focuses on the individual and contextual factors that explain why movements supposedly limited in time (called temporary) are transformed into long stays. In this research, temporary travel is approached from two perspectives: duration and law. In one case [1st empirical article], the aim is to study to what extent and for what reasons occasional stays (lasting less than one year) become the precursors of a sustainable settlement in Europe (for a period of at least one year). In the other case [2nd and 3rd empirical articles], the aim is to study how and why stays designed as temporary from a legal point of view (cases where migrants have a non-permanent right of residence) are transformed into irregular long-term stays. The thesis adopts a comparative approach that focuses on contextual effects in both three African countries of origin (Democratic Republic of Congo, Ghana and Senegal) and six European countries of destination (Belgium, United Kingdom, Netherlands, France, Italy and Spain), with a particular focus on migration policy changes. It draws on three international databases: on the one hand, the individual biographical data of the MAFE project (Migrations between Africa and Europe) and, on the other hand, two contextual databases containing a coded description of migration policy changes of the "Immigration Policy" and "Temporary vs permanent migration" projects, and the "Determinants of International Migration: A Theoretical and Empirical Assessment of Policy, Origin and Destination Effects" (DEMIG) project. The statistical methods used are, on the one hand, descriptive statistics, in particular Kaplan-Meier curves and bivariate analysis methods and, on the other hand, explanatory models, in particular discrete time risk and duration models and the logit model. In the first article, it appears that short-term stay has a positive effect on long-term migration for the three sub-Saharan flows considered, although this effect is much greater for Congolese than for Ghanaians and Senegalese. The effect of short stay migration also depends on the period for Congolese migrants, while this interaction is not significant for Senegalese migrants and Ghanaian migrants, which indicates not only the context of the country of origin modulates the effect of the short stay on sustainable migration, but also the variation of the context over time within the same country of origin can modify the relationship between short stay and long term migration. In addition, it is noted that the level of education, land and house ownership, unemployment in the country of origin, social networks and studies in Europe seem to favour the relationship between short and long stays, but economic activity and employment in the countries of origin seem to have the opposite effect. The second article revealed that the risk of being in an irregular situation was increased in periods when migration policies were becoming increasingly strict. The influence of the entry period is very clear for Ghanaian and Senegalese migrants, but the risk of being in an irregular situation decreased in the 1990s and 2000s among Congolese migrants, suggesting that migrants from a country in conflict benefit from some protection against irregularity. The risk of being in an irregular situation is higher in recent immigration countries (Italy and Spain) than in traditional immigration countries (France and the United Kingdom). The irregularity also depends on the individual characteristics and circumstances of departure for Europe. The third article unexpectedly revealed that only policies aimed at limiting entry appear to have a significant effect on the transition to irregularity of Senegalese migrants already legally entering France, Italy and Spain. This result suggests that when policies to control entry become more stringent, migrants no longer dare to leave for fear of not being able to return. Other contextual elements also influence the irregularity of migrants: a negative effect of Senegal's annual GDP growth on the transition to irregularity (immigrants would choose to return to the country to work, thus avoiding irregularity), but a positive effect of the host country's annual GDP growth on the transition to irregularity (they would remain there to benefit from growth despite irregularity).

Keyphrases: transition, short stay, temporary movement, sustainable migration, long stay, irregularity, migration policies, irregular migration, irregular stay