Network formation and efficiency in linear-quadratic games: An experimental study

We experimentally study effort provision and network formation in the linear-quadratic game characterised by positive externality and complementarity of effort choices among network neighbours. We compare experimental outcomes to the equilibrium and efficient allocations and study the impact of group size and linking costs. We find that individuals overprovide effort relative to the equilibrium level on the network they form. However, their payoffs are lower than the equilibrium payoffs because they create fewer links than it is optimal which limits the beneficial spillover effects of effort provision. Reducing the linking costs does not significantly increase the connectedness of the network and the welfare loss is higher in larger groups. Individuals connect to the highest effort providers in the group and ignore links to relative low effort providers, even if those links would be beneficial to form. This effect explains the lack of links in the network.