Progression from one pay grade to the next (e.g. 2nd class to 1st class) is internal to the university, and entails an increase in salary and responsibility. In Law, Political Science, and Economics, it is possible to be recruited directly as a full professor by passing the "agrégation" (distinct from the secondary school system's "agrégation", more widespread). Consequently, some scholars become professors without prior experience as a Maître de conférences. This remains rare however, most of the time the aggregation is a way to accelerate career advancement for the Maîtres de conférences (this is known as the "voie courte", or short way, as opposed to the "voie longue"). The French Ministry of Higher Education and Research provides a comparative table for faculty ranks in France and worldwide. For example, "professeur" corresponds to (full) professor in North America and the UK, while "maître de conférences" corresponds to (tenured) associate professor in North America, or to lecturer/reader/senior lecturer in the UK depending on pay grade and whether the habilitation was obtained or not. There also exist equivalent ranks as state employees (non civil service) for professors coming from industry and working part-time in a university. These ranks are "maître de conférences associé" (MAST) and "professeur des universités associé" (PAST), depending on academic experience. Despite the similarity, "associé" is not synonymous with "associate" (an associate professor is a mid-seniority professor, where a "professeur associé" is a part-time professor) and would be closer to adjunct. There also exist permanent, research positions, without teaching duties. They are offered by certain public research institutions, the Public Scientific and Technical Research Establishments, for instance the French National Centre for Scientific Research (CNRS), the Institute of Research for Development (IRD), the National Institute of Health and Medical Research (INSERM), or the French Institute for Research in Computer Science and Automation (Inria). Again, people in these positions are civil servants (thus, in this sense, tenured). Their statute is governed by the Decree #83-1260 of December 30, 1983. There are two levels, matching those of the teaching-research staff   The main differences between these research positions and the faculty positions are, of course, the absence of teaching duties, and the ability to move between different labs (for example, a CNRS researcher can request to move to any CNRS lab in France or abroad, whereas a faculty member is employed by a specific university).