We propose a model in which di¤erences in socioeconomic and labor market outcomes between ex-ante identical countries can be generated as multiple equilibria sustained by di¤erent beliefs on the value of e¤ort for …nding jobs. To do so, we study the incentive to improve ability in a model where heterogeneous …rms and workers interact in a labor market characterized by matching frictions and costly screening. When effort in improving ability raises both the mean and the variance of the resulting ability distribution, a complementarity between workers' choices and …rms' hiring strategies can give rise to multiple equilibria. In the high-e¤ort equilibrium, heterogeneity in ability is larger and induces …rms to screen more intensively workers, thereby con…rming the belief that e¤ort is important for …nding good jobs. In the low-e¤ort equilibrium, ability is less dispersed and …rms screen less intensively, which con…rms the belief that e¤ort is not so important. The model has novel implications for wage inequality, the distribution of …rm characteristics, productivity, sorting patterns between …rms and workers, and unemployment rates that can help explain observed di¤erences across countries.JEL Classi…cation: E24, J24, J64