We study a dynamic general equilibrium model in which firms choose their investment level and capital structure, trading off the tax advantages of debt against the risk of costly default. Bankruptcy costs are endogenous, as bankrupt firms are forced to liquidate their assets, resulting in a fire sale if the market is illiquid. When the corporate income tax rate is positive, firms have a unique optimal capital structure. In equilibrium, firms default with positive probability and their assets are liquidated at fire-sale prices. The equilibrium features underinvestment and is constrained inefficient. In particular there is too little debt and default.

We investigate the socially optimal design of financial networks, that allows to tackle the trade-off between risk sharing and contagion. We identify conditions on the shock distribution under which full integration or maximal segmentation is optimal. We also show that, under different conditions, the optimal network displays different levels of strength of linkages to other firms or intermediate degrees of segmentation. In the latter case, the individual and social incentives to establish linkages are not necessarily aligned. When firms face heterogeneous distributions of risks, they should optimally form linkages only with firms facing risks of the same kind.

We study a dynamic general equilibrium model in which firms choose their investment level and capital structure, trading off the tax advantages of debt against the risk of costly default. Bankruptcy costs are endogenous, as bankrupt firms are forced to liquidate their assets, resulting in a fire sale if the market is illiquid. When the corporate income tax rate is positive, firms have a unique optimal capital structure. In equilibrium, firms default with positive probability and their assets are liquidated at fire-sale prices. The equilibrium features underinvestment and is constrained inefficient. In particular there is too little debt and default.

We investigate the socially optimal design of financial networks, that allows to tackle the trade-off between risk sharing and contagion. We identify conditions on the shock distribution under which full integration or maximal segmentation is optimal. We also show that, under different conditions, the optimal network displays different levels of strength of linkages to other firms or intermediate degrees of segmentation. In the latter case, the individual and social incentives to establish linkages are not necessarily aligned. When firms face heterogeneous distributions of risks, they should optimally form linkages only with firms facing risks of the same kind. Received November 8, 2014; editorial decision April 28, 2017 by Editor Itay Goldstein.