Much of language economics is about the effect of linguistic variables on economic ones, studying for example, the impact of language skills on earnings. However, some research is devoted to the reverse causal direction, and the situation of minority languages is a case in point: How can we explain the decline, survival and, more rarely, the revitalization of “small” languages, and what does economics—not just in terms of explanatory variables, but also in terms of analytical approach—contribute to our understanding of the processes at hand? This question establishes a direct connection with the selection, design and evaluation of language policies, which plays a central role in this chapter. After clarifying the notion of “minority language”, we present a model of minority language use reflecting the usual sociolinguistic situation of their speakers, namely, the fact that they are typically bilingual and in addition to their minority language, often have an excellent command of a majority language. This model enables us to derive the formal conditions needed for minority language protection and promotion measures to be effective. These conditions are then transposed into a set of guidelines for language policy. The chapter concludes with a discussion that moves beyond the issue of minority language protection and promotion in given contexts of bilingualism and addresses the more general question of the value of aggregate linguistic diversity, of which minority languages constitute essential components.