Is the coexistence of Catalan and Spanish possible in Catalonia?

We study the stability of Catalan and Spanish coexistence in Catalonia, a key political and economic European region. Recent, abundant empirical data of language use is analyzed within an analytic model of population dynamics. This model contemplates the possibilities of both long-term language coexistence and decline. The data needs to be interpreted under different circumstances. The most likely scenario, we find, is a sustained coexistence. Extreme cases still lead to the decline of one of the tongues-we delimit when this can happen. Asymptotic behavior is often an unreliable predictor in complex social systems; we make an attempt at forecasting fractions of speakers towards 2030. These also suggest sustained coexistence, but some counterintuitive dynamics are unveiled. Model parameters estimated from the data convey relevant information about the prestige and interlinguistic similarity of both tongues. We quantify these parameters rigorously for these languages for the first time. Remarkably, Spanish is found to have a larger prestige in areas which historically had larger Catalan monolingual communities. With limited, spatially-segregated data we examine more fine grained dynamics, thus better addressing the likely outcomes. Differences in model parameters across regions reveal how the two languages are perceived in more urban or rural environments.