The ability to measure and forecast the value generated by tourism is today a key strategic lever for destination governance. Starting from the analysis of hospitality reservation data - occupancy, rates, purchase windows and demand dynamics - and the monitoring of tourist and residential expenditure, we will show how to arrive at a holistic vision of the economic impact on the territory, applicable to both micro-territorial contexts and large destinations. Furthermore, through the integration of heterogeneous sources and the use of forecasting models, we will analyse the methodologies for estimating the effects on tourist expenditure, flows, seasonality and return for the local economy. The presentation will highlight how timely and reliable data enable destinations, authorities and operators to anticipate scenarios, support strategic decisions and concretely measure the value produced by tourism, strengthening a true culture of data oriented towards sustainable development.