It doesn't matter, 2% or 3% is just splitting hairs. I also apparently underestimated the percent of US GDP going to federal taxes; it's around 19%, not 10%. So

It doesn't matter, 2% or 3% is just splitting hairs. I also apparently underestimated the percent of US GDP going to federal taxes; it's around 19%, not 10%. So there is still more a lot more new tax money coming in than is necessary to service the new debt. "3.9% of GDP invested initially" How is this investing 3.9% of GDP? It costs 0$ in investment for the government to issue new bonds. The only way federal debt costs the country is in the interest spent on servicing it. As long as the tax base increases faster than the interest spent on servicing debt (and also accounting for population growth) there is no economic problem with increasing the federal debt. And again, I am not arguing that the things we are spending the government money on are rational. I think we could do a lot better by cutting military spending and increasing funding for non-military research and infrastructure without deficit spending (which is certainly possible). But technically the current deficit spending is not unsustainable