How markets react when hidden debt comes to light

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. Figure 1. Sovereign risk spreads climb steadily after hidden debt is revealed 2. The size of the hidden debt is not the whole story It is tempting to assume that the larger the concealed liability, the larger the market reaction. But in our sample, the link between the size of the revealed debt and the spread response is weak. The two extremes make the point: Senegal had the largest revision in our sample, yet its market reaction was far from the worst. Mozambique’s “tuna bond” revelation involved a more modest revision but triggered the sharpest repricing of any episode, with spreads jumping by roughly 700 basis points within three months (Figure 2). Mozambique's case stands out because the borrowing appeared deliberate and covert — when the loans came to light, the IMF suspended its program and donor support collapsed, compounding the market shock well beyond what the debt figures alone would have warranted. 3. Credibility matters too How governments handle hidden debt after it is revealed matters as much as the revelation itself. We split the episodes into two groups: those where authorities promptly reconciled the newly revealed liabilities, with independent validation within a year (Dominican Republic, Türkiye, Ecuador, and Pakistan), and those where the true debt picture remained contested or the audit process dragged on (Zambia, Mozambique, and Senegal). The difference is stark. Where reconciliation was prompt, spreads rose about 123 basis points after 60 days, and much of the initial increase later reversed. Where it was delayed or contested, spreads climbed about 324 basis points and remained elevated for longer (Figure 3). Markets price not only the debt they see but also the uncertainty about what else might still be hidden. Prompt, verifiable disclosure helps close that uncertainty; delay keeps it alive and costly. With only seven episodes, the evidence on the role of reconciliation should be viewed as suggestive. But the pattern points to an important policy implication. Hidden debt is costly the moment it surfaces, but those costs are not sealed at the point of revelation — what governments do in the days and weeks that follow also matters. Markets are not simply pricing a larger debt stock; their response may also depend on how much they trust the numbers still on the page. A government that moves quickly and invites independent verification can help limit the increase in borrowing costs, while one that delays faces more persistent market repricing. The lesson is not only that transparency can reduce the risks associated with hidden debt — it may also help contain the costs once hidden liabilities come to light. For further details, please see Sovereign Risk Repricing after Hidden-Debt Revelations.