Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Région et Développement 151-176 MAROC SENEGAL 2012 fdi:010087068 ENG Région et Développement 1267-5059 https://www.documentation.ird.fr/hor/fdi:010087068 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2023-07/010087068.pdf 35 Horizon (IRD) 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. 100RETRA ; 096ENTRE ; 094CONSO