@DiegoBeghin @MisuseCase @Alon @kentwillard Like a lot of plans, you have an end state in mind where everything's hunkydory. If everyone's a migrant, there's no left-behind to trouble us. But how does the transition to that exalted stat work, when for now at least 30-40% will not for the foreseeable join the program? 1/

@DiegoBeghin @MisuseCase @Alon @kentwillard You can tell a just-so story about migrants making life better for those who remain. The marginal product of workers decreases in quantity, so those who remain will have better, more productive jobs, so everyone will be better off! 2/

@DiegoBeghin @MisuseCase @Alon @kentwillard At the same time, the migration destinations aren't underpopulated places, but huge cities. Here the just-so story is agglomeration effects mean that in fact the marginal product increases in the number of humans! 3/

@DiegoBeghin @MisuseCase @Alon @kentwillard Empirically, just-so story 2 seems pretty definitively to win, under our current economic arrangements. Places that depopulate do poorly in aggregate, and the people who live there do poorly on average and at median. Place that populate, and the people who live there do well at least on income grounds, though high costs blunt the benefit. 4/

@DiegoBeghin @MisuseCase @Alon @kentwillard That's not to say these things wouldn't work out differently with different economic and social arrangements. Place-based policy could make both just-so stories true in their respective places. Which is why I support it. /fin