Source: Munnell, A. H. 1990. Why has productivity growth declined? Productivity and public investment. New England Economic Review Jan./Feb.: 3-22.
Source: Baltagi, B. H., S. H. Song, and B. C. Jung. 2001. The unbalanced nested error component regression model. Journal of Econometrics 101: 357-381. https://doi.org/10.1016/S0304-4076(00)00089-0.
Public capital productivity data.