Abstract
Returns to labour mobility have too often escaped the attention they deserve as conduits of important forces in macro-labour models. These returns are shaped by calibrations of productivity processes that use theoretical perspectives and data sources from (i) labour economics and (ii) industrial organisation. By investigating earlier prominent studies, we conclude that the focus on firm size dynamics and shocks intermediated through neo-classical production functions in (ii) yields large returns to labour mobility that are robust to parameter perturbations. In contrast, the reliance on statistics in labour economics to calibrate per-worker productivity processes in (i) can give rise to fragilities in the sense that parameter perturbations that generate similar targeted statistics can have very different implications for returns to labour mobility.