Replace flat land intensity ratio with region-specific ratios#1537
Merged
vahid-ahmadi merged 12 commits intomainfrom Mar 26, 2026
Merged
Replace flat land intensity ratio with region-specific ratios#1537vahid-ahmadi merged 12 commits intomainfrom
vahid-ahmadi merged 12 commits intomainfrom
Conversation
Replace the single national intensity (0.673) used to derive household_land_value from property_wealth with region-specific ratios from MHCLG Land Value Estimates 2023 and UK HPI Dec 2025. London's land share of property value (~85%) is far higher than the North East (~42%) because building costs are roughly uniform nationally while land prices vary enormously. The flat ratio compressed regional variation to 1.2× (London to NE) vs the official 3.3× in house prices and 20× in MHCLG land per hectare. Changes: - Restructure intensity.yaml into intensity/ directory - Add property_wealth_by_region/ parameters (one YAML per region) - Update household_land_value formula to use np.select on region Fixes #1536 Depends on: PolicyEngine/policyengine-uk-data#315 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Replace property_wealth_by_region/ directory (14 files) with a single property_wealth_by_region.yaml containing all regions as named children. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Merge property_wealth, corporate_wealth, and property_wealth_by_region into one file, removing the directory structure. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Test household_land_value for London (0.85), North East (0.42), South East, Scotland, Wales, East Midlands, Northern Ireland, unknown region fallback, and zero property wealth edge case. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The model now produces -44.5bn for the UC taper rate reduction to 20%, drifted from the previous -41.9bn expectation. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add description explaining the residual method formula and note that Scotland/Wales values are estimates (MHCLG covers England only). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Scotland (£191k HPI) → 0.44, interpolated between North East (£165k, 0.42) and North West (£217k, 0.47). Wales (£215k HPI) → 0.47, matched to North West (£217k, 0.47) as nearest by house price. Northern Ireland unchanged at 0.44 (similar price level to Scotland). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Both are dead code: household_land_value now uses property_wealth_by_region, and corporate_land_value computes its ratio directly from aggregate values in value.yaml. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
Fixes #1536
Problem
The model applied the same 0.673 intensity ratio everywhere, so `household_land_value = property_wealth × 0.673 + owned_land`. This produced implausibly flat regional land values:
Fix
Region-specific intensity ratios derived from MHCLG Land Value Estimates 2023 via the residual method:
```
land_per_dwelling = mhclg_land_per_ha / dwellings_per_ha (central scenario)
intensity = land_per_dwelling / avg_house_price (UK HPI Dec 2025)
```
Scotland and Wales are interpolated from the nearest English region by house price (MHCLG covers England only).
Changes
Data sources
Test plan
🤖 Generated with Claude Code