The TRA project is a unique research approach based on the nationwide collection of historical individual-level data on the personal, occupational and economic situation of people having married or died between the early nineteenth century and the mid-twentieth century. Coinciding with the release of the first part of the data produced by the project, this article looks at the project’s founding principles and sources before going on to assess its geographical and temporal representativeness. Taking as an example the trend in the proportion of individuals leaving no wealth behind when they die, as established using the database, a tool such as this provides an interesting basis for writing an economic history that is both micro- and macro-social. Our analysis then shows how the approach adopted for the TRA project can be extended to any new individual-level data. This is the very principle and purpose of the TRA project, which, far from being closed, is a matrix for studying the transformations that have affected French society and many other societies over the last two centuries.