People often claim to be concerned about income-inequality statistics in the U.S.
Question: If incomes are generally rising in the U.S., and we are importing dirt-poor people from Mexico and Central America, wouldn't that have a large effect on the statistics for those at the bottom? And thus artificially raise the level of disparity between the middle and upper classes and the poorest people?
Importing more poor people masks the progress the U.S. makes in fighting poverty.
This is just a point on how one should react to those income-inequality statistics, not a point on immigration. In fact, the immigrants themselves, while poor by U.S. standards, are better off -- and become moreso over time and generations.
Of course, as each new group comes in and starts at essentially 0, that cohort is further behind the previous groups because of the growing wealth in the U.S. This just means that the immigration effect further skews these income-inequality stats with the passage of time.