The aim of this thesis is to study through four essays the economics of migration from developing countries. The …rst chapter assesses the e¤ect of natural disasters (mainly due to climate change), in developing countries, on migration rates and looks at how this e¤ect varies according to the level of education of people. Our results show that natural disasters are positively associated with emigration rates and also involve the migration of highly skilled people. The second chapter presents the di¤erent channels explaining the intention to migrate illegally. One of the novelties of the analysis is that it uses a tailor-made survey among urban Senegalese individuals. We …nd that potential illegal migrants are willing to accept a substantial risk of death and tend to be young, single and with a low level of education. We also show that the price of illegal migration, migrant networks, high expectations, tight immigration policies and the preferred destination country all play a role in the willingness to migrate illegally. The third chapter completes the second one by studying the role of risk-aversion and discount rate in illegal migration from Senegal. Our results show that these individual preferences matter in the willingness to migrate illegally and to pay a smuggler. Finally in the fourth chapter, we are interested in the e¤ect of migrants on credit markets in a rural Senegalese context. According to our results, having a migrant in a household increases both the likelihood of having a loan and its size, whether the loan is formal or informal. We also …nd that this positive e¤ect remains signi…cant no matter if the loan is taken for professional activities or simply to buy food.