SUMMARY – Civil society organisations (CSOs) developed a new benchmarking exercise to assess and compare levels of budget transparency across countries in order to address a specific transparency problem: budget information may be available, but it is not useful. Since 2001, CSOs and academic institutions have implemented the Latin American Budget Transparency Index (Índice Latinomericano de Transparencia Presupuestaria – LABTI) to measure not only the accessibility of budget information, but also its usefulness. As a perceptions-based exercise, LABTI innovates by surveying not only budget specialists, but also the variety of stakeholders that use budget information. An exercise like this one allows governments to assess if the information they are publishing is useful, while also promoting citizen participation and creating a budgetary culture, and giving a variety of actors a tool to push for transparency reforms. This Brief describes the distinctive features of this index, concrete changes LABTI has achieved and the key factors underpinning the tool’s successful use, all in an effort to offer useful lessons learned for other contexts.