Karl Smith agitates for open borders:
Immigration temporarily dilutes expenditures on Social Security, Medicare, and interest on the national debt. However, temporary counts for a lot. The future is inherently uncertain and so truly pushing off consequences into the future is inherently a net gain. There is a chance of catastrophe, in which case your sacrifices were useless and there is a chance of explosive growth, in which case your sacrifices were unnecessary. These are real possibilities and should not be ignored.
It also gives additional time to prepare for changes in Social Security. One possibility is that the continued shift away from physically intensive jobs will mean that in 50 years a retirement age of 70 is feasible even if in 25 years it is not.