Spanish sociolinguistics has many very accurate tools available to describe the situation of its bilingual areas. Some of these tools count the number of speakers of Spanish and of the other co-offcial languages. Since 1975, the Autonomous Communities' governments have promoted statistical knowledge of the linguistic reality through specific projects and sociolinguistic research. In this article, the most important projects dealing with the socio-linguistic situation of bilingual areas are introduced, along with several proposals to improve this kind of information.