In this paper, we consider a discrete-time version of the endogenous growth model developed by Barro [Barro, R.J., 1990. Government spending in a simple model of endogenous growth. Journal of Political Economy 98, 103–125], but augmented in order to envisage a public participation in the production of private goods. Public dividends are invested in order to provide a public good; in turn, the public good plays a role of indispensable production externality and, eventually, of growth engine.

For what concerns the production of private goods, we find that an optimal policy is always based on a positive participation of the government as shareholder; also, when growth is slow, a public intervention or large substitution effects stabilize the economy.

A right mix of short-run services and long-run infrastructures is suggested in slow economies to rule out expectation-driven fluctuations. Infrastructures are mainly recommended in presence of moderate income effects, while services are recommended in presence of strong income effects.