Sustainable Investment Ceilings for Cultural Infrastructure in a Shrinking Society: A Socio-Economic Evaluation of the Sendai Music Hall Project (2026–2050)

This study provides a rigorous socio-economic assessment of the proposed 64.6 billion-yen Sendai Music Hall and Disaster Memorial complex. Unlike traditional long-term evaluations, this analysis fixes the evaluation period ($T$) at 24 years (2026–2050), aligning with the statistical reliability limits of high-precision population projections from the Regional Economy Society Analyzing System (RESAS). Using a 567-pattern exhaustive simulation based on Ministry of Internal Affairs and Communications (MIC) standards, we calculated the Social Net Benefit ($W$) across varying discount rates and seating capacities. Furthermore, primary field data (visual surveys and travel time measurements) were integrated to assess functional redundancy with existing facilities such as Tohoku University’s Kawauchi Hagi Hall. The results demonstrate that any investment exceeding 5 billion yen results in a significant "social deficit", rendering the current 64.6-billion-yen plan fiscally irrational and a substantial burden on future generations.