On-the-job learning and earnings : comparative evidence from Morocco and Senegal /Nordman, Christophe Wolff, F.C. In this paper, we consider a model of on-the-job learning where workers learn informally by watching and imitating colleagues. We estimate the rate of knowledge diffusion inside the firm using two matched worker-firm data sets from Morocco and Senegal. We rely on non-linear least squares to estimate the structural parameters of the informal learning model and account for firm heterogeneity using firm factors derived from a principal component analysis. We find that the rate of knowledge diffusion is around 7 percent in Morocco and Senegal, but part of the learning-by-watching returns stems from firm heterogeneity. Informal training significantly affects the shape of returns to tenure in these two countries. Finally, we estimate an extended model with both learning-by-watching and learning-by-doing and find significant benefits from imitating colleagues in Morocco. 2012 text https://www.documentation.ird.fr/hor/fdi:010087068 fdi:010087068 Nordman Christophe, Wolff F.C.. On-the-job learning and earnings : comparative evidence from Morocco and Senegal. 2012, 35, 151-176 EN MAROC SENEGAL