> Why do workers remain in low-productivity areas when they could experience wage gains elsewhere? While the literature has proposed a few explanations, including the high cost and risky nature of migration, this column uses the case of China to examine instead the role that pollution plays. It finds that severe pollution can induce workers to relocate from productive to unproductive regions, suggesting that pollution control, coupled with policies facilitating migration, has the potential to bring about extra economic gains in developing countries.