We show the possibility of negative nominal interest rates in a general equilibrium model with financial intermediation. We establish that the decentralization of the planner’s steady state requires a zero nominal lending rate on bank loans to firms, as well as a negative nominal lending rate on central bank loans to banks. We also find that implementing the planner’s steady state requires firms to be bound by collateral requirements that limit their leverage. The key driver of the results is the very defining characteristic of banking, namely banks’ ability to create money by opening deposit accounts that borrowers can withdraw from, and that are unbacked by household deposits. Our results can be used to rationalize the ultra-low rates policy implemented by major central banks in the second half of the 2010’s and early 2020’s.

We investigate the welfare properties of the one-sector neoclassical growth model with uninsurable idiosyncratic shocks. We focus on the notion of constrained efficiency used in the general equilibrium literature. Our characterization of constrained efficiency uses the first-order condition of a constrained planner’s problem. This condition highlights the margins of relevance for whether capital is too high or too low: the factor composition of income of the (consumption-) poor. Using three calibrations commonly considered in the literature, we illustrate that there can be either over- or underaccumulation of capital in steady state and that the constrained optimum may or may not be consistent with a nondegenerate long-run distribution of wealth. For the calibration that roughly matches the income and wealth distribution, the constrained inefficiency of the market outcome is rather striking: it has much too low a steady-state capital stock.