PFS-05 - Infrastructure & Digital Backbone Constraints. PFS-05 examines how digital and physical infrastructure constraints limit the diffusion of frontier technologies and widen the productivity gap between leading and lagging regions. While prior papers in the Productivity Frontier Series analyze absorptive capacity, workforce systems, capital geography, and organizational transformation, this paper focuses on the foundational layer that enables all others: the national infrastructure backbone. The report identifies seven binding constraint areas—last-mile broadband, cloud and edge compute access, data interoperability, grid reliability, logistics bottlenecks, cybersecurity preparedness, and fragmented financing models—and traces the mechanisms through which they translate into higher adoption costs, elevated operational risk, and geographic concentration of gains. PFS-05 proposes a coordinated national strategy built around four pillars: strategic investment in digital public infrastructure, regulatory modernization and interoperability standards, capability-building through regional extension networks, and blended finance mechanisms to crowd in private capital. The objective is to convert infrastructure from a localized competitive advantage into a distributed public good that lowers marginal adoption costs across firms and regions. As part of the broader Productivity Frontier Series, this paper positions infrastructure not as a sectoral issue but as a systemic lever for restoring broad-based productivity growth between 2025–2035. Upcoming: AAA - 05 - Why Moral Responsibility Survives the Death of Consciousness (5 Mar). Upcoming: SMTS - 05 - Healthcare Access and the Stability of Economic Mobility (10 Mar).