A cohort is a group of first-time enrolled PhD students, and a new cohort group is formed each academic year (2013/14, 2014/15, 2015/16, 2016/17, etc.). Each cohort is tracked over a period of three years. Students will remain in the cohort in which they began for as long as they are registered on the same PhD programme, regardless of interruptions of study. The progressive number of cohorts is provided by the Italian law and is equal for all PhD programmes in Italy (e.g. the cohort commencing in A.Y. 2014/15 is the 30th cohort).