It’s Michael Clemens on labor mobility, so I can recommend it without having read it yet:
Clemens, Michael A.. 2011. “Economics and Emigration: Trillion-Dollar Bills on the Sidewalk?” Journal of Economic Perspectives, 25(3): 83–106.
Abstract: What is the greatest single class of distortions in the global economy? One contender for this title is the tightly binding constraints on emigration from poor countries. Vast numbers of people in low-income countries want to emigrate from those countries but cannot. How large are the economic losses caused by barriers to emigration? Research on this question has been distinguished by its rarity and obscurity, but the few estimates we have should make economists’ jaws hit their desks. The gains to eliminating migration barriers amount to large fractions of world GDP—one or two orders of magnitude larger than the gains from dropping all remaining restrictions on international flows of goods and capital. When it comes to policies that restrict emigration, there appear to be trillion-dollar bills on the sidewalk.