Policy prescriptions for poor developing countries struggle to expand employment opportunities toraise their income levels. Among these are the MENA Arab countries that have recently experiencedan unprecedented tide of popular uprisings following the rising poverty, inequality and exclusion, muchof which is related to the labor market. Since the flow approach to labor markets has become the basic toolbox to modern labor economics, this thesis has at its central insight explaining the functioning ofthose specific labor markets, particularly the Egyptian and Jordanian, using the search equilibrium theory. It looks at analyzing job accession, separations and mobility trends. Overall, evidence of highlevels of rigidity is revealed. The impact of introducing flexible employment protection regulations in these rigid markets is then discussed both empirically and theoretically. Findings show that lowering firing costs in Egypt increased significantly the job separations, but had no impact on job creations.This partial failure of the liberalization reform is interpreted theoretically by a crowding out effect due to increased corruption set up costs or increased public sector wages. A novel theoretical matching model a la Mortensen Pissarides is developped allowing for the existence of public, formal private and informal private sectors, reflecting the particular nature of developing countries. Workers’ movements up the job ladder is then explored through a structural estimation of the frictional parameters in a job search model a la Burdett Mortensen. These markets are found to have very high levels of search frictions especially among the young workers. Given the non-availability of panel data to study labor market flows, longitudinal retrospective panel datasets are extracted from the Egypt and Jordan Labor Market Panel Surveys. These panels are then compared to available contemporaneous crosssectional information, showing that they suffer from recall and design measurement erros. An original methodology is therefore proposed and developped to correct the biased labor market transitionsboth on the aggregate macro-level, using a Simulated Method of Moments (SMM), as well as on themicro-individual transaction level, using constructed micro-data weights.