For example, high-school teachers licensed in a particular state will often have to re-apply for licensure to be able to teach in another state.18 Nunn (2016) and Johnson and Kleiner (2017) have found evidence that licensed workers are less likely to change states than non-licensed workers. See for instance the analysis by Goldhaber (2015). Licensing would hence potentially weigh on participation in the low licensing states by reducing the mobility of displaced workers to other states.