This paper evaluates optimal public investment and fiscal policy for countries characterized by limited
tax and debt capacities. We study a non stochastic CRS endogenous growth model where public expenditure
is an input in the production process, in countries where distortions and limited enforceability result
in limited fiscal capacities, as captured by a maximal effective tax rate. We show how persistent differences
in growth rates across countries could stem from differential public finance constraints, and differentiate
between the case where the public expenditure finances the flow of recurring spending (such as law
enforcement), versus the stock of tangible public infrastructure. Although the flow of public expenditure
raises productivity, the government should not borrow to finance it as the resulting increase in public
debt would lower welfare and the growth rate. With outstanding public debt, the optimal fiscal policy
should keep the debt-to-GDP ratio constant in the economy with or without a binding constraint on
tax revenues as a share of GDP - current non-durable public goods should be financed only from current
revenue. With investment in the stock of public infrastructure, public sector borrowing to finance
the accumulation of public capital goods may allow the economy to reach a long-run optimal growth
path faster. With a binding tax capacity constraint, if the ratio of the initial public/private sector stock
of capital is smaller than the sustainable balanced growth ratio, the optimal policy for the government
is to purchase public capital, financed by debt, to immediately attain the sustainable ratio of public
capital to private capital. The sustainable steady-state ratio is endogenous to the initial public-to-private
capital ratio, the tax capacity and any exogenous debt limit (say, due to sovereign risk). With capital
stock adjustment costs, these statements apply to a transition of finite duration rather than an instantaneous
stock jump. With either a binding exogenous debt limit or solvency constrained borrowing, a more
patient country will have a higher steady-state growth rate but a lower steady-state public-to-private
capital ratio.