How IMF, OECD, ECB and World Bank projections depend on 2026 Brent assumptions of $86–105
ABSTRACT
Four international projection rounds published between April and September 2026 assumed 2026 oil prices between $86 and $105. This simulation argues that the gap reflects oil being treated as an exogenous input frozen at different cut-off dates, and maps what each assumption requires of the remaining months. Using World Bank Brent averages for January–August, it computes the September–December average each annual assumption needs and runs three conditional branches without probabilities. The ECB’s $89.5 requires about $86.3 for the rest of the year, below September levels. Under a branch at the OECD’s $105, 2026 averages about $95.8; if that level persists into 2027, it removes the oil decline on which IMF and ECB disinflation paths rest.
1. Purpose and method
Between April and September 2026, the World Bank, the IMF, the ECB and the OECD published growth and inflation projections that rest on visibly different oil price paths. The claim of this simulation is that these differences come from two technical choices rather than from different diagnoses of the oil market: oil enters the models as an input, and each round freezes that input on a different cut-off date. A cut-off date is the day on which market data used in a projection are fixed; later developments do not enter the projection before publication. Assumption dependence here means that a forecast outcome is more sensitive to the assumed path of an exogenous variable than to the model’s internal dynamics.
The literature explains why conditioning on a single path is fragile. Baumeister and Kilian (2016) show that each oil price episode since 1973 arose from a different mix of supply and demand forces, which is why prices keep surprising forecasters. Känzig (2021) finds that oil supply news identified around OPEC announcements raises prices immediately while production falls only gradually, with effects on US activity, prices and inflation expectations. In 2026 conditions, a few weeks of news between cut-off and publication can therefore invalidate an assumption. The method below computes the price path required for each assumption to hold and maps three branches for the September–December average. The branches are conditional; no probabilities are assigned.
2. The published baseline
| Institution and date | 2026 oil assumption | 2027 oil assumption | Main outputs |
|---|---|---|---|
| World Bank, 28 April | Brent annual average $86 | not given | energy prices +24% |
| IMF, 8 July (futures of 10 June) | $89.27 (average of Brent, Dubai Fateh, WTI) | $78.70 | world growth 3.0% / 3.4%; inflation 4.7% / 3.9% |
| ECB, 10 September (cut-off 19 August) | Brent $89.5 | Brent $78.0 | HICP 3.0% / 2.5% |
| OECD, 23 September | Brent Q4 2026 average $105 | not given | world growth 2.9% / 3.0%; G20 inflation 4.1% / 3.6% |
Sources: World Bank (2026a); International Monetary Fund [IMF] (2026a); European Central Bank [ECB] (2026); Morocco World News (2026).
Part of the $86–105 range is a difference of measure. The OECD figure is a quarterly average and the other three are annual; the IMF series averages three crudes; the OECD inflation figure covers the G20. The World Bank assumption is a war timetable rather than a market view: it assumed acute disruption would end in May 2026 and Hormuz traffic would return to pre-war levels towards the end of the year (World Bank, 2026a). The second-quarter Brent average of $104.4 invalidated the first step of that timetable.
Realised World Bank Brent averages are $80.5 for the first quarter, $104.4 for the second, $83.4 for July and $90.9 for August (World Bank, 2026b). September observations sit higher: physical Dated Brent reached $113.48 on 9 September (International Energy Agency [IEA], 2026), and the Bank of England recorded Brent at $106 on its 17 September meeting day, 36% above the level at its July Report (Bank of England, 2026).
3. The identifying assumption set
1. January–August sum: quarterly averages weighted by three months each, 80.5 × 3 + 104.4 × 3 + 83.4 + 90.9 = 729.0, an eight-month average of $91.1.
2. Annual average for a September–December average X: (729.0 + 4X) / 12.
3. Required X for an annual assumption A: (12A − 729.0) / 4. This gives $86.3 for the ECB, $75.8 for the World Bank and, approximately because of the series difference, $85.6 for the IMF.
4. 2027 oil change embedded in each round: ECB 78.0 / 89.5 − 1 = −12.8%; IMF 78.70 / 89.27 − 1 = −11.8%.
5. Static energy weight in euro area HICP: in August energy contributed 1.29 percentage points at 14.3% energy inflation (Eurostat, 2026), so 1.29 / 14.3 = 0.090. Each 10 points of energy inflation adds about 0.9 points to headline at that weight.
The link from Brent to euro area energy inflation, which includes gas, electricity and taxes, is not identified in the sources. The simulation therefore reports oil gaps and the static weight, and does not convert one into the other.
4. Branch A: the September spike reverses
Condition: Brent averages $86.3 from September to December.
Mechanism: the ECB’s annual assumption survives intact, and the projection’s falling path from $89.5 to $78.0 stays the basis for headline inflation peaking at 3.6% in the fourth quarter and energy inflation turning negative in 2027 (ECB, 2026). Arithmetic: (729.0 + 4 × 86.3) / 12 = 89.5. The IMF assumption also roughly holds; the World Bank’s is exceeded by 89.5 − 86 = $3.5.
The branch requires a four-month average about 19% below the Bank of England’s $106 reading of 17 September (86.3 / 106 − 1 = −18.6%).
Indicators: the World Bank’s monthly Brent averages for September and October; the EIA outlook on 6 October; the IEA report on 14 October.
5. Branch B: prices stay at the August average
Condition: Brent averages $90.9 from September to December.
Mechanism: the annual gap is small, but the 2027 decline grows. Arithmetic: (729.0 + 4 × 90.9) / 12 = $91.05 for 2026, which is $1.55 above the ECB, about $1.78 above the IMF and $5.05 above the World Bank. Against $91.05, the ECB’s $78.0 for 2027 now implies a 14.3% fall rather than 12.8%, so 2027 disinflation relies more heavily on the war-end assumption.
Indicators: the ICE Brent forward curve, which on 22 July priced the December 2026 contract at $84.10 and December 2030 at $70.44 (CMB News Editorial, 2026); any change in its slope shows whether the market still prices the decline the institutions assume.
6. Branch C: the OECD fourth-quarter level prevails
Condition: Brent averages $105 from September to December, matching the OECD’s fourth-quarter assumption.
Mechanism: the annual assumption error becomes material and the 2027 disinflation premise fails. Arithmetic: (729.0 + 4 × 105) / 12 = $95.75, which is $6.25 above the ECB, about $6.48 above the IMF and $9.75 above the World Bank. If 2027 Brent then averages near this level instead of falling to $78.0, the 12.8% decline built into the ECB path disappears. At the August weight, every 10 points by which euro area energy inflation exceeds the ECB path add about 0.9 points to headline HICP.
Growth does not follow mechanically. The OECD raised its 2026 world growth forecast by 0.1 point to 2.9% and cut 2027 by 0.1 point to 3.0% in the same round in which it assumed $105 (Morocco World News, 2026). A net growth revision depends on non-oil components moving at the same time.
Indicators: the oil assumption in the IMF’s October round; a revision of the ECB’s fourth-quarter inflation peak.
7. Failure conditions and limitations
The January–August average weights quarterly figures by three months each, which approximates the monthly series. The IMF comparison is approximate because its series includes Dubai Fateh and WTI. Branch C applies a quarterly OECD figure to four months, including September. The energy weight is a single-month contribution ratio, not a pass-through coefficient. The simulation says nothing about whether the IMF will change its method; the exact publication day of the October World Economic Outlook was not confirmed in the sources reviewed.
8. Outlook: Türkiye, Saudi Arabia and the World
For Türkiye, assumption dependence is visible in the Medium-Term Programme of 6 September, which raised the 2026 year-end inflation forecast from 16% to 28.4% while the CBRT estimated the war’s direct and indirect effect at about 7 points (Euronews Türkçe, 2026). The sources reviewed do not state the programme’s oil assumption, so the September price moves cannot be tested against it from outside. Publishing it would make the conditional nature of the 2027 targets readable.
For Saudi Arabia, the 2027 pre-budget statement of 30 September projects a 3.6% contraction in 2026, 12.8% growth in 2027 and a deficit of 3.6% of GDP (Asharq Al-Awsat, 2026). By inference, that growth rate requires a large output recovery, which ties it to the same condition as the institutions’ falling 2027 oil path: an end to Hormuz restrictions.
Globally, the IMF and World Bank Annual Meetings in Bangkok on 12–18 October (IMF, 2026b) are the first point at which the July forecasts of 3.0% growth and 4.7% inflation are expected to be updated with the oil assumption. Whether the cut-off falls before or after the September moves can by itself move the oil assumption by gaps of the size shown in Branch C.
9. Conclusion
The 2026 oil assumptions of the four institutions differ mainly because they were frozen on different dates and in different measures. The ECB’s $89.5 needs a September–December average of about $86.3, below September observations; the World Bank’s $86 needs about $75.8. Under the OECD’s $105, the 2026 average reaches $95.75. Oil-to-growth transmission is not mechanical, while 2027 disinflation in the IMF and ECB rounds is largely inherited from a falling oil path that assumes the war ends. October projections should be read together with their cut-off date, oil series and war timetable.
SOURCES
Asharq Al-Awsat. (2026, 30 September). Saudi Arabia earmarks $371 bn in spending for 2027 budget. https://english.aawsat.com/business/5324473-saudi-arabia-earmarks-371-bn-spending-2027-budget
Bank of England. (2026, 17 September). Bank Rate maintained at 3.75% – September 2026 Monetary Policy Summary and Minutes. https://www.bankofengland.co.uk/monetary-policy-summary-and-minutes/2026/september-2026
Baumeister, C., & Kilian, L. (2016). Forty years of oil price fluctuations: Why the price of oil may still surprise us. Journal of Economic Perspectives, 30(1), 139–160. https://doi.org/10.1257/jep.30.1.139
CMB News Editorial. (2026, 22 July). Brent backwardation steepens as product markets tighten again. Commodity Market Board. https://commodity-board.com/brent-backwardation-steepens-as-product-markets-tighten-again
Euronews Türkçe. (2026, 6 September). Türkiye enflasyon hedefini revize etti: 2026 yıl sonu beklentisi yüzde 16’dan yüzde 28,4’e yükseldi [Türkiye revised its inflation target: 2026 year-end expectation raised from 16% to 28.4%]. https://tr.euronews.com/2026/09/06/turkiye-enflasyon-hedefini-revize-etti-2026-yil-sonu-beklentisi-yuzde-16dan-yuzde-284e-yuk
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International Monetary Fund. (2026b). 2026 Annual Meetings. https://www.imf.org/en/meetings/2026/annual
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Morocco World News. (2026, 23 September). OECD raises 2026 global growth forecast to 2.9% amid energy and inflation risks. https://www.moroccoworldnews.com/2026/09/339493/oecd-raises-2026-global-growth-forecast-to-2-9-amid-energy-and-inflation-risks/
World Bank. (2026a, 28 April). Middle East war to spark biggest energy price surge in four years [Press release]. https://www.worldbank.org/en/news/press-release/2026/04/28/commodity-markets-outlook-april-2026-press-release
World Bank. (2026b, 2 September). World Bank commodity price data (The Pink Sheet), September 2026. https://thedocs.worldbank.org/en/doc/74e8be41ceb20fa0da750cda2f6b9e4e-0050012026/related/CMO-Pink-Sheet-September-2026.pdf
Furkan Mahmut Tameroglu