Funzione sociale e valore delle biblioteche pubbliche: alcuni riscontri recenti della valutazione d’impatto in campo internazionale

The article presents a critical overview of the recent international literature and case studies in the field of impact evaluation of public libraries. Several relevant trends emerge from the review. First, there is an increasing attention for assessing outcomes related to library services. Second, national surveys are expanding constantly. Third, transnational surveys are being tested. This work is completed with some comments on survey methods, on research results and on prospects of Italian Library and Information Science in the field of evaluation.