Sylvain Catherine@sc_cath• almost 2 years ago

This is a result you could get in any economic model with decreasing return to learning and huge variability in talent. In such a model, kids would all converge to different skill levels but similar marginal return to effort/time. Think about firms instead of kids. They can have very different levels of efficiency in their technology or management. Yet, they should have the same marginal productivity of labor because they would increase their size until hiring one additional worker increases revenues by less than the market cost of labor. Hence, at the margin, they are all the same. This is the standard way economists think about firm heterogeneity. You can easily follow the same reasoning for kids. Even if their ability to learn varies greatly, they may all converge to a level of knowledge at which it’s equally hard, boring… to learn one more thing. That level would be higher for gifted kids yet you’d observe that they all marginally learn at the same speed. By contrast, if there is huge variability in learning opportunities you’d observe the opposite in the data. The kids that have been under-stimulated would learn faster at the margin and catch up with those that have already received lots of support.