One of the underlying assumptions of the improvements to society from ease of migration comes from the fact that the models assume homogenous works. While there may be gains to productivity from easier migration, it doesn’t mean that workers will necessarily adapt to their surroundings. In Borjas’s book, We Wanted Workers, he points out the implications of psychic costs on movers and argues that it’s not fair to assume all workers who move will be as productive as they were at their source. This bit from Ryan Hamilton echoes that sentiment that allowing for migration may not mean productivity gains will occur if workers are unable to adjust to their new surroundings.