Will Wilkinson and The Economist offer some thoughts on immigration and poverty, made fresh by Robert Samuelson's current column:

It takes a special kind of brazenness to propose a reduction of the national poverty rate at the expense of ensuring that more people stay poor by denying them opportunity to set foot in the nation.

If Mr Rector cared about actual human poverty, as opposed to some statistic about the number of Americans beneath what he agrees is an arbitrary line, he’d favour an increase in legal immigration and some kind of guest-worker program. If these policies were to inflate American poverty rates, as they surely would, that would be something to be proud of. From a humanitarian perspective, if a wealthy nation’s poverty rate improves, then it isn’t letting enough poor people in.

At some point, it's plausible to argue that the change in the number of poor people, and the depth of their poverty, might change the character of America for the worse in a way that gives us the moral authority to restrict their entry. But I don't think it's plausible to say that we've reached that point yet.