Making connections: access and market competition with public broadband

We use causal forests to examine how public utility broadband providers are associated with broadband adoption and local market structure across 194 counties in Tennessee and Iowa, 38 of which have a public utility broadband provider. Public provider presence is associated with an average 6% point higher broadband adoption share, lower private-carrier market shares, and lower measured market concentration, though the latter partly reflects the mechanical effect of an additional provider on the concentration index. The estimated adoption difference is largest in lower-income and urban counties and in counties where public providers have greater geographic reach and offer lower prices. Given the cross-sectional design, limited number of treated counties, and the observable income imbalance between treated and untreated counties, we interpret these results as a transparent, explicitly associational account of structured heterogeneity in broadband outcomes rather than as causal estimates; sensitivity analyses indicate that the income heterogeneity patterns are not driven solely by the observable selection margin.