The childless should pay enough to ensure there are younger people to do the work of supporting the childless when retired.

Using foreigners to fill a demographic shortfall is unsustainable/shortsighted.

That said, I'm in New Zealand and too many young adults emigrate because (A) our economy sucks and (B) richer economies like to employ NZ citizens (NZers love international travel/work).

more than people who have children? that's logical. you get cuts for the hard work you're doing.