Government debt, bond supply and the cost of sovereign borrowing

macroPublished 19 October 20262 min readfixed income, macro

Key points

• The OECD says public debt has risen sharply after successive crises and that long-term sovereign yields have risen further.
• It describes 30-year yields as elevated to levels unseen in the past decade or two. It does not give the percent on the page cited here.
• The IMF's October 2026 outlook lists fiscal vulnerabilities among downside risks and argues for rebuilding policy space.
• A debt ratio this site has not taken from a table is not filled in.

What is going on

Governments finance deficits by issuing liabilities. Investors buy those liabilities at a yield. A higher yield raises the cost of new borrowing and of debt that is rolled over. It does not rewrite the coupon on debt already issued unless that debt is floating or indexed. The OECD says higher long-term rates are raising government borrowing costs and weighing on equity valuations. The IMF says fiscal frameworks have to cope with shocks and that debt-financed corporate tax cuts can have cross-border effects. Both are arguments from named reports. Neither is a WiT Markets debt forecast.

Why it matters

Bond supply can raise the term premium even when the central bank's policy rate is unchanged. That is a different event from a policy hike, and it can coincide with one, as in September 2026 when the Federal Reserve and the ECB both raised policy rates while the OECD was describing elevated long yields. Sorting the policy-rate piece from the premium piece requires the yield and the policy rate side by side. This note has the policy decisions in companion articles and does not have the yield.

What to watch

A usable debt discussion names the country, the measure (gross or net), the currency and the source table. Sustainability is then a question about the interest rate, the growth rate and the primary balance, not a slogan. The OECD asks for multi-year fiscal strategies whose pace depends on the country. That is a recommendation, not evidence that any named government has adopted one.

Risks

Investor demand, regulation and the currency of issuance can overwhelm a simple supply story. A higher yield with stronger nominal growth is not the same fiscal problem as a higher yield with weaker growth. This note refuses the debt-to-GDP figure that would make the discussion look finished.