The French pension system is characterised by its highly complex regulatory framework and by the very wide diversity of career profiles of its members. In this context, and in order to best carry out its missions of producing statistical information and shedding light on public policies in the area of pensions, DREES, the Health and Solidarity Ministerial Statistical Department, collects data from the various schemes on a sample of contributors and on a sample of pensioners. Since 2010, DREES has been developing a dynamic microsimulation model based on these two inter-regime samples. TRAJECTOiRE was created through the juxtaposition of three modules: the first models professional careers, the second simulates retirement ages and the third calculates retirement pensions. The development of each new module was made necessary by the limitations of the pre-existing tools. As a particularly rich model, TRAJECTOiRE has since been used on numerous occasions.

Many other institutions, such as INSEE, the main pension schemes and certain government departments and research institutes, have adopted similar models. Although this diversity leads to a fragmentation of resources, it is also an asset for understanding and managing the French pension system.