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greenbook provides cost-benefit analysis primitives from
the HM Treasury Green Book: the kinked STPR, discount factors, NPV,
equivalent annual cost, GDP-deflator rebasing, optimism bias,
distributional weights and monetised valuation.
All bundled parameter tables carry vintage metadata. Inspect with:
gb_data_versions()
#> dataset
#> 1 stpr_schedule
#> 2 gdp_deflator
#> 3 optimism_bias
#> 4 metb
#> 5 wellby
#> 6 vpf
#> 7 qaly
#> 8 carbon_values
#> source
#> 1 HM Treasury Green Book supplementary guidance: discounting (updated 28 October 2026), paragraph 3.8; pre-October 2026 schedule from the 2003 Green Book
#> 2 HM Treasury, GDP deflators at market prices, and money GDP: October 2026 (Budget), calendar-year series, 2025 = 100
#> 3 HM Treasury Supplementary Green Book Guidance: Optimism Bias (Mott MacDonald 2002)
#> 4 HM Treasury Green Book 2018 and 2022 (the 2026 edition specifies no uplift; see chapter 6 Costs of raising public funds)
#> 5 HMT Wellbeing Guidance for Appraisal (July 2021)
#> 6 DfT Transport Analysis Guidance (TAG) data book v2.03FC (December 2025), Table A4.1.1, WTP element for fatal casualties
#> 7 DHSC Supplementary Green Book Guidance + NICE HTA thresholds
#> 8 DESNZ Valuation of Energy Use and GHG Emissions for Appraisal (November 2023), Data Tables 1-19, Table 3
#> last_updated
#> 1 2026-10-31
#> 2 2026-10-31
#> 3 2026-04-26
#> 4 2026-04-26
#> 5 2026-04-26
#> 6 2026-04-26
#> 7 2026-04-26
#> 8 2026-04-26
#> notes
#> 1 Vintage 2026-10 (default): 3.00/2.50/2.25 percent for years 1-30/31-75/76-125, no discounting beyond year 125, no health or catastrophic variants. Vintage 2003: 3.5/3.0/2.5/2.0/1.5/1.0 percent with health and catastrophic-risk variants.
#> 2 Outturn 1990-2025 (ONS Quarterly National Accounts, 30 September 2026). Forecast 2026-2031 chained from OBR October 2026 EFO growth rates; type column marks forecast years.
#> 3 Indicative upper bounds for capex and duration uplift across six project categories. Values unchanged since 2003.
#> 4 Uplift on revenue raised through distortionary taxation. 20 percent in 2018 onwards (was 30 percent historically).
#> 5 WELLBY central value GBP 13000 in 2019 prices (low/central/high range). Convert to other base years via gb_deflator().
#> 6 Anchor 2023 = GBP 2,474,341 (WTP component). Other years derived by 2 percent annual real GDP per head growth per TAG methodology.
#> 7 GBP 70k per QALY in 2024 prices for cross-government appraisal. NICE thresholds GBP 20k-30k retained for HTA context.
#> 8 Single consolidated series (replacing historical traded / non-traded split). Low / central / high paths 2020-2050 in 2022 prices, GBP/tCO2e.The Green Book Social Time Preference Rate is 3.00 percent for years
1 to 30, 2.50 percent for years 31 to 75 and 2.25 percent for years 76
to 125, following HM Treasury’s update of 28 October 2026.
gb_stpr() returns the rate for any year:
gb_stpr(c(10, 30, 31, 75, 76, 125))
#> [1] 0.0300 0.0300 0.0250 0.0250 0.0225 0.0225
gb_schedule_table()
#> year_from year_to standard health catastrophic
#> 1 0 30 0.0300 NA NA
#> 2 31 75 0.0250 NA NA
#> 3 76 125 0.0225 NA NAHM Treasury advises against discounting beyond year 125, so the
default schedule stops there. The schedule in force before October 2026,
with its health and catastrophic-risk variants, is available as
vintage = "2003" for reproducing earlier appraisals:
gb_stpr(c(10, 30, 31, 75, 76, 200, 300), vintage = "2003")
#> [1] 0.035 0.035 0.030 0.030 0.025 0.020 0.015
gb_schedule_table(vintage = "2003")
#> year_from year_to standard health catastrophic
#> 1 0 30 0.035 0.0150 0.0300
#> 2 31 75 0.030 0.0129 0.0257
#> 3 76 125 0.025 0.0107 0.0214
#> 4 126 200 0.020 0.0086 0.0171
#> 5 201 300 0.015 0.0064 0.0129
#> 6 301 1000 0.010 0.0043 0.0086gb_discount_factor() applies the kinked schedule
annually using prod(1 + r_t):
gb_discount_factor(0:5)
#> [1] 1.0000000 0.9708738 0.9425959 0.9151417 0.8884870 0.8626088
gb_discount_factor(c(0, 30, 31, 75, 76))
#> [1] 1.0000000 0.4119868 0.4019383 0.1356155 0.1326313The kink is correctly handled across band boundaries:
A simple appraisal: capex of GBP 100 in year 0, annual benefits of GBP 30 from year 1 to year 9.
costs <- c(100, rep(0, 9))
benefits <- c(0, rep(30, 9))
appraisal <- gb_npv(benefits - costs, base_year = 2024)
appraisal
#>
#> ── Green Book appraisal ────────────────────────────────────────────────────────
#> NPV (real, standard schedule): "GBP 133.6"
#> Horizon: 10 years (year 0 to 9)
#> Base year: 2024
#> Vintage: Green Book "2026-10"The result is a gb_appraisal object with full
provenance. Use summary() for a more detailed view:
To compare options of different durations, annualise the NPV:
gb_real() converts nominal values at year-of-occurrence
prices to real values at a chosen base year:
gb_real(nominal_values = c(100, 110, 120),
year = 2020:2022,
base_year = 2024)
#> [1] 117.4778 128.4301 132.4863gb_rebase() does the same operation between two
real-terms base years:
gb_deflator() exposes the underlying factor:
v0.2.0 adds optimism bias (Mott MacDonald upper bounds), distributional weights, and Marginal Excess Tax Burden. v0.3.0 ships the valuation library: WELLBY, VPF, QALY, DESNZ carbon values. See the package GitHub repository for the full roadmap.
These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
Health stats visible at Monitor.