Matt Welch: I have never had anxiety about debt-to-GDP. It's never been anything on my radar. The conversation I'm trying to have today is the amount of federal spending, including interest payments as a percent of the GDP. He says if you were cared about only that, then refinancing the debt is in equally valid proposition and changing the duration. Welch: If for no other reason than our debt service is going to crowd out whether you want more guns or more butter in our federal budget.