Immigration: Porter’s numbers are excellent. This isn’t the first article I’ve seen that suggests that a more porous border might actually decrease illegal immigration. (The stronger the border, the more likely immigrants are to stay if they make it across. Otherwise they come, earn what they can, and return home because they know they can come back if they [economically] need to.)
Unions: When is a union not a union? A little-know (nowadays) subset of the union question. This sort of thing was more common when more people were in unions. Businesses don’t need to do this now; too few people are unionized for it to matter much.