UK NSDP/NPDP Historical Time Series, 1945–2025, with Cross-Country Decompositions — Dataset and Reproduction Code

Principal empirical dataset accompanying the book The GDP Illusion: Two New Measures of Productive Output — NSDP and NPDP (John Blackburn, 2026). The book decomposes GDP via the proved identity GDP = NSDP + (S − P) + P, where NSDP (Net Sustainable Domestic Product) is GDP minus all trading of existing assets and NPDP (Net Property Domestic Product) is GDP minus the property-trading subset. The headline measure is the productive-output ratio ρ = NSDP/GDP. For the United Kingdom it falls from 0.998 in 1945 to a nadir of 0.871 in 2007 and recovers only partially to 0.908 in 2025. Cross-country decompositions (2024/2025) give Germany 0.957, South Korea 0.945, Japan ≈0.930, China 0.927, United Kingdom 0.908, United States 0.906. The package contains an Excel workbook (UK 1945–2025 series; cross-country decompositions; house-price speculation σ derivation; financial speculation S−P derivation; metadata; figure-data sheets) and a Python reproduction script (openpyxl only) that reconstructs the UK series from documented inputs and verifies the accounting identity for every observation.