That's my answer to this question:
ObSF: “Guesting Time” by R. A. Lafferty.
During the 2000 primary season, I made it a point to ask each presidential candidate in person the following question at least once:
Current immigration policy is doubling US population within the lifetimes of today’s children. Since you support this policy, will you at least say when we should stop?
One billion people? Two billion? Three?