Philip, you've given this careful thought, and I applaud that. So many don't dig beneath the surface of this issue. I'd like to suggest a couple other reasons any nation should aim for zero net immigration.

1. We need someone to be accountable for achieving sustainable population size. If a nation fails to address this, or has an overt or defacto open-borders policy in order to grow its economy, then it is diffusing responsibility for sustainable population size, leaving that to someone else. Who?

2. In the case of the U.S., our defacto open borders policy exploits immigrants. They are crowded into sorry living conditions, separated from their families, and poorly paid, so that we can have cheap houses, cheap landscaping, cheap food and cheap landscaping. Perpetuating this system delays by generations the day when these immigrants could stay in their homeland and have a good life.

Dave Gardner
Producing the documentary
Hooked on Growth: Our Misguided Quest for Prosperity
www.growthbusters.org