The reform, the costing, its model, and data

This article explains how microsimulation, a new ex ante assessment method, became the “gold standard” to make and evaluate the effects of socio-fiscal reform. Primarily designed under costing-obsessed administrations, microsimulation models were initially developed with a lack of coordination, prompting institutions and teams leading the development to compete as well as cooperate. At the end of the 2000s, a new chapter began. The near-monopoly of microsimulation administration began to wane as academic economists gradually returned with renewed interest in the field. This led to a redrawing of the microsimulation landscape, which, despite the existence of competing companies, affirmed the status of this tool’s monopoly on the way in which reforming the socio-fiscal system is conceived.