NEWS

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greenbook 0.1.0 (2026-04-28)

• Initial release. Implements Phase 1 to Phase 3 cost-benefit analysis primitives from HM Treasury Green Book guidance.

Discounting

• gb_stpr(), gb_discount_factor(), gb_discount(): kinked Social Time Preference Rate (standard, health, catastrophic-risk variants) and discount factors.
• gb_npv(), gb_eanc(): net present value and equivalent annual net cost.

Real-terms rebasing

• gb_deflator(), gb_real(), gb_rebase(): GDP-deflator factors and real-terms conversion against a bundled vintage.

Optimism bias

• gb_optimism_bias(), gb_apply_ob(), gb_categories(): lookups for the Mott MacDonald (2002) upper bounds across six project categories with mitigation factor support.

Distributional analysis

• gb_dist_weight(), gb_dist_weighted_npv(): iso-elastic distributional weights using Green Book default eta = 1.3.

Adjustments

• gb_metb(): Marginal Excess Tax Burden uplift with vintage lookup (20 percent in 2018+, 30 percent historical).

Valuation library

• gb_wellby(): WELLBY conversion to GBP per HMT Wellbeing Guidance (July 2021). Central GBP 13,000 in 2019 prices.
• gb_vpf(): Value of Preventing a Fatality per DfT TAG. GBP 2.153 million in 2024 prices.
• gb_qaly(): Quality-Adjusted Life Year per DHSC supplementary Green Book guidance (GBP 70k) plus NICE thresholds.

Carbon

• gb_carbon_value(): DESNZ Carbon Values for Appraisal, central / low / high paths, traded and non-traded sectors.
• gb_carbon_npv(): NPV of an emissions path with full discounting and rebasing.

High-level appraisal

• gb_appraise(): end-to-end appraisal in one call. Optionally applies optimism bias and METB to costs, then computes NPV and BCR with full provenance.
• gb_compare(): side-by-side comparison of two or more options with NPV / BCR / EANC ranking and preferred-option selection.
• gb_progression(): track an appraisal across SOC, OBC, FBC business case stages.
• gb_place_based(): aggregate sub-projects into a place-based business case (per Green Book 2026), with optional synergy uplift.
• gb_economic_case(): wrap an appraisal in Five Case Model Economic Case structure (CSFs, options, monetised summary, non-monetised, VfM, recommendation).
• gb_validate(): lint an appraisal for sign-convention, base-year, schedule, and consistency errors.

Risk

• gb_risk_register(): build a risk register with monetised exposure (probability x impact), aggregate by category, and optionally risk-adjust an appraisal NPV.

Sensitivity

• gb_sensitivity_ob(): optimism bias sensitivity sweep across a vector of mitigation factors. Required at every Green Book business case gateway.

Reporting

• gb_headline(): one-page summary with NPV, BCR, EANC, payback, and provenance.
• gb_cost_per_unit(): cost-effectiveness ratio (PV cost per QALY, WELLBY, tCO2e, etc.).
• gb_to_latex(): render an appraisal as a LaTeX table.
• gb_to_excel(): multi-sheet Excel export (requires openxlsx).
• gb_to_word(): one-page Word document export (requires officer and flextable).

Lookups and provenance

• gb_schedule_table(), gb_data_versions(): tibble of the STPR schedule and vintage metadata for all eight bundled parameter tables (STPR, GDP deflator, optimism bias, METB, WELLBY, VPF, QALY, carbon values).
• gb_appraisal S3 class with print(), summary(), format() methods. The summary() method renders BCR, optimism bias, METB, distributional eta, and unweighted NPV when present.