Sure, I picked that ratio because it makes reasoning easy since then interest rates = percentage of GDP. My point is precisely that it only works when rates ar

Sure, I picked that ratio because it makes reasoning easy since then interest rates = percentage of GDP. My point is precisely that it only works when rates are low. When rates need to go higher you can’t spend so much of your tax base on servicing debt without bad things happening. You cannot simply let the debt mature because it gets refinanced at the current rate unless you’re running a budget surplus to reduce the principal (which is generally considered unwise compared to growing/inflating out of it). Rates don’t stay low forever