This paper examines the relationship between public-sector capital and private-sector productivity, focusing on state-level data. Previous studies suggested a significant link between public capital and productivity, but the author finds no such relationship when using standard techniques to control for unobserved state-specific characteristics. Estimates that exclude such controls show substantial productivity impacts, but these are likely due to the limitations of the data rather than a true effect of public capital. The results align with growth accounting techniques, which effectively control for state-specific effects. Region-level estimates are similar to state-level estimates, suggesting no significant spillover effects across states. The analysis uses a production function model to estimate the impact of public-sector capital on private output. The model includes state-specific effects, time-specific effects, and an error term. The author tests various econometric specifications, including fixed-effects, random-effects, and instrumental variables estimators, to address potential biases. The results show that public-sector capital has no significant impact on private productivity when controlling for state-specific effects. The use of instrumental variables and first-differences also fails to show a significant effect. The paper concludes that the apparent positive relationship between public capital and productivity is an artifact of restrictive econometric frameworks. The best estimate of the elasticity of private output with respect to public capital is essentially zero. The findings suggest that aggregate data do not reveal sufficiently large linkages between public sector capital and private production activities to support the contention that government capital spillovers are the source of economy-wide variations in private productivity. Future research should focus on more precise microeconomic linkages between infrastructure provision and production processes.This paper examines the relationship between public-sector capital and private-sector productivity, focusing on state-level data. Previous studies suggested a significant link between public capital and productivity, but the author finds no such relationship when using standard techniques to control for unobserved state-specific characteristics. Estimates that exclude such controls show substantial productivity impacts, but these are likely due to the limitations of the data rather than a true effect of public capital. The results align with growth accounting techniques, which effectively control for state-specific effects. Region-level estimates are similar to state-level estimates, suggesting no significant spillover effects across states. The analysis uses a production function model to estimate the impact of public-sector capital on private output. The model includes state-specific effects, time-specific effects, and an error term. The author tests various econometric specifications, including fixed-effects, random-effects, and instrumental variables estimators, to address potential biases. The results show that public-sector capital has no significant impact on private productivity when controlling for state-specific effects. The use of instrumental variables and first-differences also fails to show a significant effect. The paper concludes that the apparent positive relationship between public capital and productivity is an artifact of restrictive econometric frameworks. The best estimate of the elasticity of private output with respect to public capital is essentially zero. The findings suggest that aggregate data do not reveal sufficiently large linkages between public sector capital and private production activities to support the contention that government capital spillovers are the source of economy-wide variations in private productivity. Future research should focus on more precise microeconomic linkages between infrastructure provision and production processes.