French OAT Yields Under a Simultaneous ECB and Fed Tightening Shock

1. The Scenario

Official data. In May 2026 the ECB’s main refinancing rate was 2.15% and its deposit rate 2.00% (ECB). The ECB has since raised rates twice, to a deposit rate of 2.50% and a refinancing rate of 2.65%. The Fed held its range at 3.50–3.75% in May and raised it to 3.75–4.00% on 16 September.

Scenario assumptions. Adding 450bp to the May refinancing rate gives 6.65%, equivalent to a deposit rate of 6.50%, the pre-shock deposit rate plus the full 450bp of the 2022–23 cycle. Adding 525bp to the Fed’s May upper bound of 3.75% gives 9.00%. From today’s ECB rates the same endpoint requires 400bp rather than 450bp. The two tightenings are assumed to occur within one macro-financial regime. Inflation eventually falls, but only after a significant contraction in demand and credit. We assume the ECB does not neutralise the sovereign-market shock through large-scale intervention, and in Scenario A fiscal credibility is preserved while in B and C it is not.

2. France’s Starting Macro-Fiscal Position

Official data: fiscal. Public debt reached €3,595.5 billion, or 119.0% of GDP, at the end of the second quarter of 2026, up from 117.5% in the first quarter; net debt was 111.4% (INSEE, 29 September). The 2025 deficit was 5.1% of GDP. The IMF projects deficits of 5.2% in 2026 and 4.9% in 2027, a primary balance of −2.7% in 2026, and gross debt of 118.5% in 2026, 120.3% in 2027 and 121.1% in 2028; the government has warned that debt could reach 121.7% in 2027. The government’s 2027 budget, presented on 1 October, aims to reduce the deficit to 5%. Interest costs are rising: general-government interest was €64.7 billion in 2025, the State’s debt charge was budgeted near €59 billion for 2026 (higher on some estimates), and the medium- and long-term borrowing programme is about €310 billion.

Growth and capacity. IMF projections put real GDP growth at 0.6% in 2026, 0.9% in 2027 and 1.2% in 2028, as the Middle East war raises inflation and weighs on domestic demand. The Banque de France’s June severe scenario has growth flat in 2026 with inflation near 4%. The IMF finds the banking sector resilient but flags political uncertainty ahead of the 2027 presidential election. How much capacity does France have to absorb a structurally higher cost of capital? Limited: low potential growth, high public spending and little fiscal room.

Maturity, external position and ratings. The average maturity of French public debt is about 8.4–8.5 years, and non-residents hold 53.8% of OATs (AFT). The 2025 current-account deficit was €11.6 billion and the net international investment position −€885.4 billion, or −29.6% of GDP, from −€704.0 billion in 2024 (Banque de France). Ratings are Aa3 negative (Moody’s, next review 23 October), A+ stable (S&P, Fitch, Scope), AA negative (DBRS) and AA− stable (KBRA) (AFT). France is not an emerging-market balance-of-payments case: it issues in euros, sits in the euro area and benefits from its aggregate external surplus. But the external position and the large non-resident holding amplify capital-flow dynamics in a global tightening.

3. Why the OAT Curve Cannot Be Derived from the ECB Rate Alone

A mechanical calculation of the May 10-year (about 3.65%) plus 450bp would give 8.15%, and from today’s 4.87% would give 9.4%. Both are analytically wrong. We use a conceptual decomposition, not an econometric identity:

Long yield ≈ expected short rates + inflation expectations + real-rate component + term premium + sovereign-specific premium. Equivalently, OAT yield = Bund yield + OAT–Bund spread. Expected short rates would rise with the policy path. Inflation expectations could first rise and later fall if recession dominates. The term premium reflects inflation uncertainty, duration supply and fiscal risk. The sovereign premium reflects fiscal credibility, politics, liquidity and investor positioning. The 2022–23 cycle is the guide to magnitude: the deposit rate rose 450bp while the 10-year Bund rose about 300bp, a beta near two-thirds.

4. The Global Duration Shock

Market data and scenario assumptions. The OAT curve is partly a domestic fiscal instrument and partly a global duration asset. On 8 October the 10-year Treasury yield closed at 5.23% after touching about 5.36%, the highest since 2002, and the San Francisco Fed puts the 10-year term premium at 1.49% (5 October), about 70% of the rise since the 16 September FOMC. In 2023 the 10-year Treasury yield stood at about 0.9 times the funds rate. A funds rate of 9% would be consistent with a 10-year Treasury yield near 8%, and the Bund has traded about 200bp below Treasuries at the peak of the previous cycle.

LBMR interpretation. A Fed funds rate near 9% would raise global real yields, the global term premium and dollar-funding costs, and would raise the opportunity cost of holding European duration. Global investors compare duration across Treasuries, Bunds, gilts, JGBs and credit, and non-residents hold more than half of OATs. The BIS also notes that leveraged, short-horizon investors have become marginal buyers of government bonds, which can amplify supply pressure. Two anchors then bracket the Bund: a policy-rate beta of about 0.75 on a 6.5% deposit rate suggests about 4.9%, and a Treasury-minus-200bp anchor suggests about 6.0%. We use 4.75–6.0% for the 10-year Bund.

5. The French Sovereign Premium

Market data. The OAT–Bund spread was about 134bp on 7 October, with the 10-year OAT at 4.83% and the Bund at 3.49% (Banque de France and Bundesbank data), and briefly above 150bp, the widest since 2011, around the 1 October budget. In May the spread was roughly 65bp (LBMR estimate from an OAT near 3.65% and a Bund near 3.0%). Of the roughly 122bp rise in the 10-year OAT since May, about 70bp is spread and about 50bp the Bund, so the French-specific premium explains more than half. The 10-year OAT has risen more than 110bp since early July, the largest quarterly rise since 1987 (Trading Economics).

LBMR interpretation. The spread can widen for fiscal deterioration, political uncertainty, debt supply, rating concerns, liquidity, foreign positioning, banking concerns, fragmentation risk and doubts about consolidation. Market pricing can deteriorate before ratings change, and the Moody’s review on 23 October and the S&P review on 27 November are catalysts. Even if Bund yields rise substantially, OAT yields can rise faster if the sovereign premium widens, which is why the interaction between monetary tightening and fiscal risk is convex.

6. The 10-Year OAT

The 10-year prices ECB expectations, inflation, Bund yields, global duration, recession expectations and the OAT–Bund spread. It is the maturity most sensitive to the policy path, and it would be the first to benefit if inflation fell and the ECB signalled an eventual reversal. At about 3.65% in May (the 2035 OAT cleared at 3.61% at the AFT auction of 7 May, interpolated to a constant 10-year maturity) and 4.87% on 9 October, it has already priced a modest part of the ECB path plus a large part of the fiscal premium. In a deep recession it would be the most responsive to falling inflation expectations, which partly offsets the sovereign premium.

7. The 20-Year OAT

The 20-year emphasises long-term monetary expectations, fiscal sustainability, term premium, debt supply and political credibility. It was about 4.2% in May (the 2046 OAT cleared at 4.22% on 7 May) and is near 5.3% in market data on 9 October. Its slope over the 10-year was about 55bp in May and about 40bp now, so the curve has flattened since May as policy-driven repricing dominated. Investors at this horizon ask whether France can stabilise debt through two decades of higher real rates, pension and defence spending.

8. The 30-Year OAT

The 30-year prices the long-run fiscal regime: structural inflation, demographics, pensions, defence and energy investment, term premium and sovereign risk. It was about 4.5% in May (the 2057 OAT cleared at 4.48%) and is 5.42% (9 October). The central thesis follows: the longer the maturity, the more the market moves from pricing monetary policy towards pricing the credibility of the sovereign’s long-term fiscal regime. The 10s30s slope has compressed from about 85bp in May to about 55bp, which suggests tightening and inflation risk have so far driven the long end more than a collapse in fiscal credibility.

9. Three Stress Scenarios

Scenario A: severe monetary tightening, fiscal credibility preserved. ECB 6.65%, Fed 9%, inflation eventually falls, consolidation is credible, banks are resilient and ECB transmission functions. The spread widens moderately to 100–175bp and the curve is flat to mildly inverted at the peak of policy.

Scenario B: monetary tightening plus fiscal fragmentation (central stress case). Same policy path, plus a major recession, weak growth, persistent deficits, rising debt and political fragmentation. The spread widens to 175–275bp and the term premium rises, steepening the long end.

Scenario C: sovereign–financial feedback loop (extreme tail). A severe recession, banking losses, liquidity deterioration and doubts about debt stabilisation. The spread widens to 275–425bp while the Bund partly rallies as a safe haven. Yields approaching or exceeding 9–10% would indicate a sovereign-risk regime, not a continuation of tightening.

Reassessment of the source estimates. Our central 10-year of about 7.75% is higher than the 7.25% in the source analysis. Anchoring on May means the Bund must carry the full policy shock, and the 2022–23 beta and the Treasury anchor give a Bund of 4.75–6.0%. Our 20- and 30-year centrals are close to the source (8.25% and 8.75%), because the compression of the curve since May is offset by a larger term premium in a fragmented-fiscal regime.

10. The Sovereign–Bank Feedback Loop

The loop runs: OAT yields up, OAT prices down, losses in bank and institutional portfolios, tighter financial conditions, credit contraction, lower GDP, a wider deficit, higher debt, a higher sovereign premium and higher OAT yields. The IMF finds French banks resilient, and non-residents hold more than half of OATs, so a first-round hit falls on global investors as well as domestic ones. The ECB’s May Financial Stability Review notes that non-bank investors hold more than half of long-dated euro-area government bonds and that vulnerabilities among them could amplify stress. The loop can be broken by bank resilience, credible fiscal consolidation or ECB intervention, and in 2022–23 banking stress arrived through duration, with the March 2023 turmoil breaking at a 2.50% deposit rate.

11. Debt Dynamics and the r−g Problem

Illustrative mechanics. Market yields do not equal the effective rate on the stock. At 119% of GDP, a 100bp rise in the average rate would add about 1.2% of GDP in annual interest once fully passed through, and 300bp about 3.6%. With a borrowing programme near 10% of GDP a year, a 300bp rise on new issuance would add roughly 0.3% of GDP to interest costs in the first year and reach about 1.5% after five years under these static assumptions. These are mechanical illustrations, not forecasts. The debt-stabilising primary balance is approximately the debt ratio times (r−g): with r−g of 1pp it is about 1.2% of GDP, 2pp about 2.4%, 3pp about 3.6% and 4pp about 4.8%, against a primary balance of −2.7% in 2026 (IMF).

Why France is more exposed. The effective interest rate on French debt is about 2–2.4%, roughly equal to nominal growth of about 2–2.5%, so r−g is near zero today. As new debt is priced at 7–9% while recession pushes nominal growth towards zero, the marginal r−g could be 5pp or more. The same shock would be much less dangerous for a sovereign with a debt ratio below 60% and a primary surplus.

Weaker growth has two opposing effects on yields: lower inflation and lower expected policy rates push yields down, while weaker revenues, higher deficits and a higher sovereign premium push them up. This tension runs through every scenario, and the outcome depends on which dominates. In A and early in B the first dominates the curve at the front; in B and C the second dominates the long end.

12. ECB Policy Constraints

A 6.65% refinancing rate with French yields at 9–10% sets inflation control against sovereign-market stability and monetary transmission. The Transmission Protection Instrument exists for disorderly dynamics, but its eligibility depends on sound fiscal and macroeconomic policies and compliance with the EU fiscal framework; France is in an excessive deficit procedure that the authorities aim to exit by 2029. Bundesbank President Nagel said on 1 October that the instrument addresses price-stability risks, not spread levels. We do not assume the ECB would automatically rescue France, and we do not assume it would remain passive in a disorderly market. Conditionality limits moral hazard, while the risk of fiscal dominance grows as interest costs rise. At what point does fighting inflation become constrained by sovereign-market stability? Probably earlier in a high-debt, fragmented-politics scenario than a conventional inflation-targeting framework would suggest.

13. The New Price of Capital

The most important consequence is not that French bonds become more expensive to finance. It is that the equilibrium price of capital throughout the economy changes, and the OAT curve is the benchmark through which this is transmitted. Euro-area bank rates in August stood at 3.77% for corporate loans and 3.60% for mortgages (ECB), and the September repricing is not yet in those data. A move of 300–400bp in the benchmark could re-price fixed-rate mortgages, corporate investment, infrastructure, private equity and credit, bank lending, equity multiples, real-estate values and pension liabilities. It would also raise the hurdle rate for public investment in energy, defence and infrastructure at the same time as the fiscal room shrinks, so fiscal policy becomes a function of the price of capital.

14. Asset-Class and Market Implications

These are macro-financial transmission channels, not investment recommendations.

• OATs: duration risk and spread risk compound; curve shape signals which dominates.
• Bunds: safe-haven bid in C, but a global-duration loser in A and B; relative performance versus OATs widens.
• Equities: higher discount rates compress multiples; earnings weaken; dispersion by leverage and rate sensitivity.
• Banks: securities losses and funding costs offset by margins; credit deterioration; sovereign exposures.
• Real estate and corporate credit: higher mortgage rates, lower valuations and investment; wider spreads and refinancing pressure.
• Euro and gold: ECB tightening supports the euro but global dollar strength and sovereign stress pull the other way; gold responds to real yields and credibility, as its fall of about a quarter from the January record shows.

15. Monitoring Dashboard

16. What Would Falsify the Scenario?

The severe estimates would be too high if inflation normalised quickly, nominal growth proved stronger, consolidation became credible and debt began to fall, the OAT–Bund spread narrowed, foreign demand for OATs strengthened, the ECB intervened, the global term premium fell, Fed tightening produced a rapid disinflationary recession, or euro-area external balances strengthened. Scenario C would be invalidated if banks proved resilient, the spread stayed below about 200bp, auctions remained well covered and the Moody’s and S&P reviews passed without downgrades. Evidence already leans against the extreme tail: the IMF finds the banking sector resilient, auctions have cleared and the spread, though elevated, is well below Scenario C levels.

Conclusion

The key question is not whether the ECB can raise rates by 450bp. It is what happens to a highly indebted sovereign when the global equilibrium price of capital rises sharply at the moment growth weakens. For France the answer depends on whether monetary tightening remains a cyclical shock, which it would in Scenario A, or becomes a challenge to the credibility of the long-term fiscal regime, as in B and C. The May-to-October experience shows the second channel is already active: more than half of the 122bp rise in the 10-year OAT is the French-specific premium. That is why the OAT curve is best read as the transmission mechanism between monetary tightening and the changing price of capital, and why the long end, which prices fiscal credibility, is where the scenario would matter most.