In 1982, the decentralization of vocational education policy from the state to the regions, is starting in France. This process concerns not only the institutions but also the production of knowledge. From 1988, each Region may establish a regional observatory of employment and training whose mission is to produce diagnostic and prospective tools which are helpful to public policies, particularly to vocational education policies. Based on a comparison between the 2nd and 3rd regions of France - Rhône-Alpes and Provence-Alpes-Côte d'Azur (PACA)-, this paper analyses the role of knowledge production in the regulation of policy making (Commaille Jobert, 1998), from a socio-historical perspective (Thelen, 2003). Taking into account the changing socio-political contexts, the study of the two observatories is designed to reflect the dynamics of ideas and their influence on regional policies. To analyse the relationship between ideas, knowledge and action, five dimensions are identified (Palier and Surel, 2005): the diagnosis of problems, the values and objectives, the standards for action, the instruments, the cognitive images and reference models (eg, lifelong learning replaces, over time, the adequacy of training for employment).