Governments sometimes borrow more than they publicly admit. Loans taken out by state-owned companies, debts guaranteed behind closed doors, payments owed to contractors but never recorded — these liabilities can accumulate for years without appearing in any official figure. To outside observers — investors, credit rating agencies, international lenders — the public balance sheet can therefore look stronger than it really is. Then, suddenly, that picture changes.
Recent research has shown that such “hidden debt” can be large. It tends to come to light in one of three ways: an incoming government inherits the books and discloses what it finds; an international audit or IMF review uncovers discrepancies; or a financial crisis forces a full accounting of what the state actually owes. When that moment arrives, the numbers can be startling — in some countries, reported public debt burden has been revised upward by billions of dollars. But the revelation itself is only the beginning. What happens next — to borrowing costs, to investor confidence, and to a country’s ability to access financing — is less well understood. Do markets react immediately or gradually? Do reactions differ depending on how the government responds? And how persistent are the effects?
To answer these questions, we examined seven well-documented episodes of hidden debt coming to light between 2005 and 2025 in the Dominican Republic, Ecuador, Mozambique, Pakistan, Senegal, Türkiye, and Zambia tracking daily borrowing costs and stripping out global market swings to isolate each country’s specific experience. The results highlight important differences in how markets respond to hidden-debt revelations — and offer clear lessons for governments navigating the aftermath.
Three lessons emerge.
1. Borrowing costs rise steadily, and the reaction builds for weeks
Markets do not anticipate revelations — borrowing costs are broadly unchanged in the 10 days leading up to these events. Once the information becomes public, however, the cost of borrowing rises sharply and persistently. On average, spreads widen by about 80 basis points within 10 days and by about 150 basis points by day 20, peaking at nearly 250 basis points around day 50 (Figure 1). Strikingly, the adjustment is gradual. By day 10, less than half of the eventual two-month repricing has occurred, and spreads stay elevated well into the second month. Investors appear to spend weeks reassessing not only the larger debt burden but also how promptly the country’s fiscal reporting is revised.
READ MORE: https://blogs.worldbank.org/en/developmenttalk/how-markets-react-when-hidden-debt-comes-to-light
