This article investigates several linguistic changes which are ongoing in north-western Catalan using a contemporary corpus. We take advantage of a range of dialectometric methods that allow us to calculate and analyse the linguistic distance between varieties in apparent time from an aggregate perspective. Specifically, we pay attention to the process of structural dialect loss due to linguistic advergence to standard and eastern Catalan in many north-western Catalan dialects located in Catalonia (Spain) and Andorra. We also provide evidence that the dialect leveling taking place in these two areas strongly contrasts with the relative stability of the Catalan dialects on the other side of the Catalan-Aragonese border in Spain, where Catalan is not an official language. These opposite sociolinguistic situations (Catalonia and Andorra have strong language policies to support Catalan, whereas Aragon does not) have triggered a twofold process of vertical advergence between the Catalan spoken in Catalonia and Andorra towards the prestigious varieties, on the one hand; and of horizontal divergence between these dialects and those located in Aragon, on the other hand. This situation has notably strengthened the border differences between Aragon and Catalonia during the last 80 years. This article is one of the first attempts to study the border effects not only between regions belonging to different countries but also between different administrative regions 'within' the same country. In addition, we investigate the different roles of urban versus rural areas, providing support for the view that the spatial and hierarchical diffusion patterns are complementary.