David, Jim, Peter and Rick are after the same question in my last WSJ oped and Blog post: Suppose the Fed wants to raise interest rates with a huge debt outstanding. With, say, $18 trillion outstanding, raising interest rates to 5% means raising the deficit by $900 billion a year. That's real fiscal resources. In a present value sense, monetary tightening costs someone $900 billion a year of taxes. There is no chance that current tax revenues can go up that much, or current spending can go down that much. So, raising interest rates to 5% with a lot of debt outstanding means we will borrow it, the debt will grow $900 billion a year faster, and the larger taxes /lower spending will come someday in the far off future.
Or maybe not. David, Jim, Peter and Rick delve in to the "tipping point" I alluded to.
Countries with high debt loads are vulnerable to an adverse feedback loop in which doubts by lenders about fiscal sustainability lead to higher government bond rates, which in turn make debt problems more severe.
Southern Europe was basically on a similar death spiral until the ECB stepped in and said it would print euros to buy up any debt as needed. The big contribution of the paper: facts.
Using statistical methods, case studies and a wealth of recent data on fiscal crises, we have found that countries with gross debt above 80% of GDP and persistent current-account deficits—as is currently the case in the United States—face sharply increasing risk of escalating interest payments on their debt. This means even higher budget deficits and debt levels and could lead to a fiscal crunch—a point where government bond rates shoot up and a funding crisis ensues.The vitally important point: it's nonlinear. Evidence from times and countries with lower debts does not apply.
When the Fed raised real rates in the late 1970s, Federal debt was “only” 32% of GDP. Interest payments did swell, from 1.5% to 3% of GDP, accounting for more than half of the Reagan deficits. And long-term real interest rates were high for a decade, usually interpreted as the market's worry that we would go back to inflation, which is the same thing as saying that the government might not have the stomach to pay off all this debt. But strong growth and tax reform led the US to large primary surpluses, and we paid off that extra debt.
We go in to this one with over 100% debt to GDP ratio, and much weaker growth prospects. The experience of how "easy" tightening was in the early 1980s should not lull us in to a sense of security.
They made a small, but I think crucial omission:
With sufficient political will, the U.S. government can avoid fiscal dominance and achieve long-run budget sustainability by gradually reining in spending on entitlement programs such as Medicare, Medicaid and Social Security, while increasing tax revenue by broadening the base.Quiz question: What's missing here?
Growth. Tax revenue = tax rate x income. You can broaden the base as much as you want, without economic growth the long-term US budget is a disaster. And the current alarming projections assume that we will, someday, return to strong growth. All the reining in, soaking the rich, and base broadening in the world will not save us without growth. We prescribe "structural reform" for Greece. Why not for the US?
Note to graduate students. The theory here is actually less well worked out than you think. Suppose the Fed follows a Taylor rule, hoping to control inflation by raising interest rates when inflation breaks out. But suppose there is a Laffer limit on taxes, total tax revenue is less than T. In this paper and my own speculations there is a conjecture that inflation can get out of control, and a sense of multiple run-prone equilibria, and a sense that current debt/GDP is an important state variable. It needs better working out.