Changes in version 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.