This paper investigates the quantity of safe assets. First, we estimate that the average safe-asset ratio (ratio of safe to total assets) in 34 OECD countries was 37% in 2015. Further, we document that this ratio is relatively stable over time. Second, we build a heterogeneous-agent model with rare disasters and risk aversion coefficients that accounts for (i) the average level of the safe-asset ratio; (ii) the stability of this ratio over time; (iii) the observed risk-free rate of around 1.0% per year; and (iv) the empirical unlevered equity premium of about 4.2%. The model also replicates the observed highly concentrated distributions of wealth and equity. Finally, Ricardian equivalence holds in our model: issuing additional government bonds has no effect on rates of return and the net quantity of safe assets. Surprisingly, the crowding-out coefficient for private bonds with respect to public bonds is around -0.5, a value found in empirical studies.

A safe asset's real value is insulated from shocks, including declines in GDP from rare macroeconomic disasters. However, in a Lucas-tree world, the aggregate risk is given by the process for GDP and cannot be altered by the creation of safe assets. Therefore, in the equilibrium of a representative-agent version of this economy, the quantity of safe assets will be nil. With heterogeneity in coefficients of relative risk aversion, safe assets can take the form of private bond issues from low-risk-aversion to high-risk-aversion agents. The model assumes Epstein-Zin/Weil preferences with common values of the intertemporal elasticity of substitution and the rate of time preference. The model achieves stationarity by allowing for random shifts in coefficients of relative risk aversion. We derive the equilibrium values of the ratio of safe to total assets, the shares of each agent in equity ownership and wealth, and the rates of return …