PFS-03 - This paper is part of the Productivity Frontier Series (PFS), a multi-paper research program examining the structural constraints shaping U.S. productivity growth in the 2025–2035 period. PFS-03 analyzes the growing concentration of capital and innovation within a small number of metropolitan clusters and its implications for national productivity performance. While geographic agglomeration accelerates frontier breakthroughs, it also raises systemic barriers to diffusion, leaving many regions undercapitalized and unable to absorb advanced technologies, managerial practices, or high-value industrial activity. The paper disaggregates the capital–geography mechanism across risk capital dynamics, talent agglomeration, infrastructure, institutional ecosystems, and patient capital availability. It identifies the reinforcing feedback loops that lock investment into frontier clusters and limit spillovers to lagging regions, producing persistent productivity asymmetries despite continued technological progress. Rather than advocating for deconcentration for its own sake, PFS-03 develops a calibrated framework for rebalancing capital flows while preserving frontier dynamism. It proposes a coordinated set of public and private interventions—blended finance, absorptive-capacity building, infrastructure upgrades, regulatory modernization, and connective market design—aimed at lowering fixed costs of innovation adoption and expanding viable investment pathways outside established hubs. The paper concludes with an implementation and sequencing strategy, operational KPIs, and scenario analysis outlining the conditions under which geographic diversification of capital can translate localized innovation into broad-based, durable productivity gains. Upcoming: Delegation Is Not Distribution - Agency After Interruptibility - Essay 1 (05 Feb) Upcoming: SMTS-03 - Labor Mobility and Regional Reallocation. The Opportunity Flow Problem: Migration, Skills, and Regional Reallocation Dynamics (10 Feb) Upcoming: AAA-03 – Human-AI Hybridity Is Not New. Whats New Is the Disappearance of Accountability (12 Feb)