Digital Infrastructure Development and Corporate Labor Productivity—A Multi-Period DID Study Based on “Broadband China” Pilot Cities

Digital infrastructure may improve firm productivity, yet its economic value depends on whether firms can absorb external connectivity and embed it in production, management, and investment decisions. Using the staggered implementation of the “Broadband China” pilot policy as a quasi-natural experiment, this study examines the effect of city-level broadband infrastructure on the revenue-based labor productivity of Chinese A-share listed firms from 2009 to 2023. A multi-period difference-in-differences model shows that the pilot policy is associated with an increase in revenue per employee. The baseline estimate implies an economically meaningful increase of approximately 4.1%, and the result remains robust to alternative productivity measures, sample restrictions, stricter fixed effects, placebo tests, PSM-DID, and IPW-DID. CSDID estimates are positive but not statistically significant at conventional levels and are therefore interpreted as directionally consistent rather than independently confirmatory. Evidence based on total factor productivity, management expense intensity, and investment adjustment is consistent with production efficiency, management coordination, and organizational adjustment channels. Heterogeneity tests show stronger effects among non-state-owned, eastern region, and non-manufacturing firms. The findings suggest that broadband infrastructure generates productivity benefits when firms have the organizational absorptive capacity to convert external digital connectivity into internal operational efficiency.