is discussed with a moral vocabulary that obscures the arithmetic underneath it.
A state is not a household, because it does not retire, it can tax and it borrows in a currency it may issue.
therefore depends on a relationship between three numbers rather than on the size of the stock.
If growth exceeds the interest rate, a debt ratio falls even when a government runs a modest .
That condition held for much of the period after the financial crisis and has since reversed in several economies.
When the relationship reverses, the arithmetic becomes unforgiving and the available choices all carry political cost.
Currency of issue matters more than any single ratio.
A country borrowing in its own currency cannot be forced into and can instead suffer inflation and a falling exchange rate.
A country borrowing in a foreign currency faces a hard constraint that no domestic policy can soften.
Comparing the two cases with a single threshold ratio, as commentators routinely do, is simply an error.
matters as much as level, and is the part most often ignored.
A stock of debt that must be this year exposes a government to a market mood; one with an average of twelve years does not.
What the borrowing financed is absent from almost every published ratio.
Debt incurred to build a rail network and debt incurred to fund a temporary tax cut appear identically in the statistics.
The first raises the future capacity to service it and the second does not, which is the entire question.
written as a fixed ceiling therefore discourage exactly the spending that would make the ceiling affordable.
Several countries have moved to rules that exempt net investment, and the definition of investment immediately becomes the battleground.
Every technical fix in this field converts a political argument into a definitional one, which is progress of a modest kind.