The case of Catalonia has often been pointed out as a case of success in the field of language policy, based on
the improvement in its legal situation, the increase in the number of people who know it, and the extension of its use in certain
fields. To contribute to a complete evaluation of the current language policy model in Catalonia, this article assesses the
evolution of the first languages of the population over the last fifteen years. The study shows that during this period, despite
some oscillations, Catalan has remained in stable numbers of L1 speakers in absolute terms, thanks essentially to very strong
patterns of intergenerational transmission in both linguistically homogeneous and mixed couples. However, significant immigration
during this period has substantially increased the weight of other languages and, to a lesser degree, Castilian, so that in
relative terms Catalan has been reduced as a first language between 2003 and 2018.