dataset,source,last_updated,notes
stpr_schedule,HM Treasury Green Book 2022 Annex A6 / supplementary discounting guidance,2026-04-26,"Kinked STPR: 3.5/3.0/2.5/2.0/1.5/1.0 percent across bands at 30/75/125/200/300 years. Health and catastrophic-risk variants per supplementary guidance."
gdp_deflator,"HM Treasury, GDP deflators at market prices (December 2025 Quarterly National Accounts release, calendar-year series, 2024 = 100)",2026-04-26,"Outturn 1990-2024 from CGDP_Deflators_Qtrly_National_Accounts_December_2025_update.xlsx. Forecast years can be added via inflateR or the Spring Statement supplementary release."
optimism_bias,HM Treasury Supplementary Green Book Guidance: Optimism Bias (Mott MacDonald 2002),2026-04-26,"Indicative upper bounds for capex and duration uplift across six project categories. Values unchanged since 2003."
metb,HM Treasury Green Book 2022 chapter on real terms and Marginal Excess Tax Burden,2026-04-26,"Uplift on revenue raised through distortionary taxation. 20 percent in 2018 onwards (was 30 percent historically)."
wellby,HMT Wellbeing Guidance for Appraisal (July 2021),2026-04-26,"WELLBY central value GBP 13000 in 2019 prices (low/central/high range). Convert to other base years via gb_deflator()."
vpf,"DfT Transport Analysis Guidance (TAG) data book v2.03FC (December 2025), Table A4.1.1, WTP element for fatal casualties",2026-04-26,"Anchor 2023 = GBP 2,474,341 (WTP component). Other years derived by 2 percent annual real GDP per head growth per TAG methodology."
qaly,DHSC Supplementary Green Book Guidance + NICE HTA thresholds,2026-04-26,"GBP 70k per QALY in 2024 prices for cross-government appraisal. NICE thresholds GBP 20k-30k retained for HTA context."
carbon_values,"DESNZ Valuation of Energy Use and GHG Emissions for Appraisal (November 2023), Data Tables 1-19, Table 3",2026-04-26,"Single consolidated series (replacing historical traded / non-traded split). Low / central / high paths 2020-2050 in 2022 prices, GBP/tCO2e."
