pred-2026-03-21-061
The OBR will revise its 2026 UK GDP growth forecast below 1.0% in the Spring Statement (expected March 26, 2026), down from the October 2025 forecast of approximately 1.6%.
- created
- 2026-03-21
- resolves
- 2026-03-28
- resolved
- 2026-03-28
- outcome
- 0
- brier
- 0.4225
- base rate
- 0.45
- meta-confidence
- medium
Tradition weights
- keynesian0.37
- marxist0.28
- institutionalist0.25
- austrian0.10
Evidence for (8)
- Iran-driven energy shock compresses household disposable income through energy prices — the direct transmission mechanism into consumption contraction that OBR models will capture
- Fiscal headroom erosion since October 2025 eliminates counter-cyclical spending capacity, meaning the demand shock propagates without fiscal buffer — amplifying OBR's own multiplier estimates downward
- OBR March 2022 precedent: Russia-Ukraine energy shock forced ~2pp downward revision in a single Statement, demonstrating both institutional willingness and methodology to make large corrections under undeniable supply shocks
- Tariff escalation disrupts UK financial-services global intermediation — the sector that structurally underwrites UK GDP outperformance — at the margin
- Knightian uncertainty from Iran conflict (non-calculable, not mere risk) freezes irreversible investment decisions regardless of financing costs
- All four aggregate demand components (C, I, G, NX) simultaneously constrained or contracting: energy shock hits C, uncertainty hits I, fiscal rules constrain G, tariffs and J-curve lag compress NX
- Goldman private credit warning signals Minsky instability is live — hedge-to-speculative finance migration under cash-flow squeeze flags financial stress in OBR's financial stability assumptions
- OBR credibility as an institution depends on responsiveness to observable deterioration; defending a 1.6% forecast against undeniable compound shocks would damage its core institutional asset
Evidence against (7)
- OBR temporal smoothing behavior: if Iran shock is modeled as a 6-12 month transient rather than persistent structural disruption, the revision may land at 1.1–1.3% rather than below 1.0%
- UK GDP is ~80% services; lower energy-input intensity than manufacturing-heavy economies means pass-through from energy prices to GDP is attenuated relative to frameworks assuming a production-structure model
- LNG long-term contracts and residual energy price cap mechanisms may partially buffer the transmission of spot energy prices into OBR's energy price assumptions
- Bank of England rate-cut optionality: pre-emptive cuts could partially offset demand compression outside the fiscal channel — OBR may price in monetary offset
- Sterling depreciation from current-account deterioration theoretically provides competitiveness offset for tradeable services exports on a 12-month view — OBR might smooth this into the forecast
- Political incentives favor a 'serious but manageable' landing zone at 1.1–1.2% rather than sub-1.0%, which triggers automatic fiscal rule commentary about spending cuts or tax rises
- Automatic stabilisers (benefits, transfer payments) partially offset demand compression without violating fiscal rules — reducing the multiplied contraction the Keynesian framework emphasizes
Reasoning chain
Three of four frameworks independently converge on sub-1.0% (Keynesian 0.82, Marxist 0.73, Austrian 0.68 with caveat that OBR will understate), while the Institutionalist — the framework best-suited to modeling the OBR as an institution — assigns only 35% probability to sub-1.0%, predicting instead a 1.0–1.3% landing zone. The weighted confidence (Keynesian 0.37 × 0.82 + Marxist 0.28 × 0.73 + Austrian 0.10 × 0.68 + Institutionalist 0.25 × 0.35 = 0.660) is adjusted downward to 0.65 to reflect the institutionalist insight that OBR’s temporal smoothing methodology is a genuine off-ramp from the sub-1.0% outcome. The base rate of 0.45 is derived from the frequency with which OBR has made large single-Statement revisions that cross specific thresholds: the March 2022 episode establishes capability and willingness, but the 0.6pp threshold from 1.6% to below 1.0% is a large absolute move. Framework evidence lifts confidence from base rate to 0.65.
Philosophical basis
Keynesian framework grounds the demand-mechanics case (all four components constrained simultaneously; Knightian uncertainty suspending animal spirits; fiscal-multiplier arithmetic forcing OBR's own models to register the deficiency). Institutionalist framework provides the critical corrective on magnitude — OBR as an institution has temporal smoothing and political mediation behaviors that could prevent the revision from reaching below 1.0% even if structural fundamentals justify it. The tension between these two framings is the primary source of uncertainty.
Falsification criteria
Prediction is WRONG if the OBR Spring Statement publishes a 2026 UK GDP forecast at or above 1.0%. Prediction is CORRECT if the published figure is below 1.0%. Prediction is UNRESOLVABLE if the Spring Statement is postponed beyond 2026-04-04.
Sources
- 035-malinvestment-energy-terms-of-trade analog (ZIRP-era capital structure exposure)
- 079-bifurcation (fiscal constraint + external shock as bifurcation trigger)
- 087-decline-derivatives (OBR as institutional mortality-acknowledger — or denier)
Brier breakdown
Post-mortem
Auto-resolved (falsified, confidence=0.97). Evidence: The OBR published its Economic and Fiscal Outlook on March 26, 2026 (Spring Statement). It revised the 2026 UK GDP growth forecast down to 1.1%, from the November 2025 forecast of 1.4%. This is a downward revision, but 1.1% is at or above the 1.0% threshold specified in the falsification criteria. Sources: https://obr.uk/efo/economic-and-fiscal-outlook-march-2026/; https://commonslibrary.parliament.uk/research-briefings/cbp-10495/; https://www.investmentweek.co.uk/news/4526412/spring-statement-26-uk-growth-slow-2026-ticking. Reasoning: The OBR Spring Statement was delivered as expected and published a 2026 UK GDP growth forecast of 1.1%. The falsification criteria explicitly states the prediction is WRONG if the published figure is at or above 1.0%. At 1.1%, the forecast exceeds the 1.0% threshold, falsifying the prediction. The prediction's direction was correct (the OBR did revise downward from ~1.4-1.6%), but the magnitude was not large enough to breach the 1.0% threshold.