After years of ultra-loose fiscal, monetary, and credit policies and the onset of major negative supply shocks, stagflationary pressures are now putting the squeeze on a massive mountain of public- and private-sector debt. The mother of all economic crises looms, and there will be little that policymakers can do about it.

In the private sector, the mountain of debt includes that of households (such as mortgages, credit cards, auto loans, student loans, personal loans), businesses and corporations (bank loans, bond debt, and private debt), and the financial sector (liabilities of bank and nonbank institutions). In the public sector, it includes central, provincial, and local government bonds and other formal liabilities, as well as implicit debts such as unfunded liabilities from pay-as-you-go pension schemes and health-care systems – all of which will continue to grow as societies age.

Just looking at explicit debts, the figures are staggering. Globally, total private- and public-sector debt as a share of GDP rose from 200% in 1999 to 350% in 2021. The ratio is now 420% across advanced economies, and 330% in China. In the United States, it is 420%, which is higher than during the Great Depression and after World War II.

Of course, debt can boost economic activity if borrowers invest in new capital (machinery, homes, public infrastructure) that yields returns higher than the cost of borrowing. But much borrowing goes simply to finance consumption spending above one’s income on a persistent basis – and that is a recipe for bankruptcy. Moreover, investments in “capital” can also be risky, whether the borrower is a household buying a home at an artificially inflated price, a corporation seeking to expand too quickly regardless of returns, or a government that is spending the money on “white elephants” (extravagant but useless infrastructure projects).

Such over-borrowing has been going on for decades, for various reasons. The democratization of finance has allowed income-strapped households to finance consumption with debt. Center-right governments have persistently cut taxes without also cutting spending, while center-left governments have spent generously on social programs that aren’t fully funded with sufficient higher taxes. And tax policies that favor debt over equity, abetted by central banks’ ultra-loose monetary and credit policies, has fueled a spike in borrowing in both the private and public sectors.

Years of quantitative easing (QE) and credit easing kept borrowing costs near zero, and in some cases even negative (as in Europe and Japan until recently). By 2020, negative-yielding dollar-equivalent public debt was $17 trillion, and in some Nordic countries, even mortgages had negative nominal interest rates.

The explosion of unsustainable debt ratios implied that many borrowers – households, corporations, banks, shadow banks, governments, and even entire countries – were insolvent “zombies” that were being propped up by low interest rates (which kept their debt-servicing costs manageable). During both the 2008 global financial crisis and the COVID-19 crisis, many insolvent agents that would have gone bankrupt were rescued by zero- or negative-interest-rate policies, QE, and outright fiscal bailouts.