[rbehrends]

If you don't want them, other countries will be more than happy to take those unwanted Ph.D. students off your hands.

Ph.D. students don't pay tuition because the remuneration they get for their work is part tuition waivers, part money. If they do not work for the university and are not eligible for tuition waivers, they have to pay tuition instead (both foreigners and US Americans).

In practice, they are basically inexpensive (for their qualifications) temporary employees in teaching and research; what they get out of it is a degree.

[genwin]

If they are a net benefit to US taxpayers even when they plan to leave the US, that's a good point. We should give them a green card in advance though, plus ask their intention. There's got to be plenty of supply of worthy foreign students who intend to stay here. Taxpayer money is surely being left on the table if we are educating foreign students regardless of their intention of staying.