In our incomplete markets economy households choose portfolios consisting of risky (uninsurable) capital and money. Money is a bubble, it has positive value even though it yields no payoff. The market outcome is constrained Pareto inefficient due to a pecuniary externality. Each individual agent takes the real interest rate as given, while in the aggregate it is driven by the economic growth rate, which in turn depends on individual portfolio decisions. Higher inflation due to higher money growth lowers the real interest rate on money and tilts the portfolio choice towards physical capital investment. Modest inflation boosts growth rate and welfare.

This article studies the full equilibrium dynamics of an economy with financial frictions. Due to highly nonlinear amplification effects, the economy is prone to instability and occasionally enters volatile crisis episodes. Endogenous risk, driven by asset illiquidity, persists in crisis even for very low levels of exogenous risk. This phenomenon, which we call the volatility paradox, resolves the Kocherlakota ( 2000) critique. Endogenous leverage determines the distance to crisis. Securitization and derivatives contracts that improve risk sharing may lead to higher leverage and more frequent crises.

Forward-looking agents care about expected future utility flows, and hence have higher current felicity if they are optimistic. This paper studies utility-based biases in beliefs by supposing that beliefs maximize average felicity, optimally balancing this benefit of optimism against the costs of worse decision making. A small optimistic bias in beliefs typically leads to first-order gains in anticipatory utility and only second-order costs in realized outcomes. In a portfolio choice example, investors overestimate their return and exhibit a preference for skewness; in general equilibrium, investors' prior beliefs are endogenously heterogeneous. In a consumption-saving example, consumers are both overconfident and overoptimistic.

We propose a measure of systemic risk, Δ CoVaR, defined as the change in the value at risk of the financial system conditional on an institution being under distress relative to its median state. Our estimates show that characteristics such as leverage, size, maturity mismatch, and asset price booms significantly predict Δ CoVaR. We also provide out-of-sample forecasts of a countercyclical, forward-looking measure of systemic risk, and show that the 2006:IV value of this measure would have predicted more than one-third of realized Δ CoVaR during the 2007–2009 financial crisis.

We study a simple model of liquidity risk management in which a firm is subject to rollover risk. When a firm is unable to rollover its maturing bonds by issuing new bonds, it may have to seek more expensive sources of financing or even liquidate its assets, possibly at fire-sale prices. One way to reduce this risk is to hold excess cash reserves, which can be expensive in practice (Bengt Holmström and Jean Tirole 2000; 2001). In this paper, we focus on an alternative way of managing liquidity risk, through the optimal (dynamic) choice of the maturity structure of debt. Our analysis highlights one advantage of short-term financing. The firm, while in good financial health, can readjust its maturity structure more quickly in response to changes in its asset value. Ideally, the firm would secure long-term financing just prior to when its financial health may worsen. Through this strategy, the firm can secure financing for the longest continuous period possible without rollover failure, avoiding inefficient restructuring costs. Put differently, the objective of the firm with long-term assets is to maximize the effective maturity of its liabilities across several refinancing cycles, rather than to maximize the maturity of the current bonds outstanding.

We use data from the Panel Study of Income Dynamics to investigate how households' portfolio allocations change in response to wealth fluctuations. Persistent habits, consumption commitments, and subsistence levels can generate time-varying risk aversion with the consequence that when the level of liquid wealth changes, the proportion a household invests in risky assets should also change in the same direction. In contrast, our analysis shows that the share of liquid assets that households invest in risky assets is not affected by wealth changes. Instead, one of the major drivers of household portfolio allocation seems to be inertia: households rebalance only very slowly following inflows and outflows or capital gains and losses.

Optimal Beliefs, Asset Prices, and the Preference for Skewed Returns by Markus K. Brunnermeier, Christian Gollier and Jonathan A. Parker. Published in volume 97, issue 2, pages 159-165 of American Economic Review, May 2007

China's gradualistic approach allowed the government to learn how the economy reacts to small policy changes, and to adjust its reforms before implementing them in full. With fully developed financial markets, however, private actors may front-run future policy changes, making it impossible to implement policies gradually. With financial markets, the government faces a time-inconsistency problem. The government would like to commit to a gradualistic approach, but after it observes the economy's quick reaction, it has no incentive to implement its policies in small steps.

We propose a simple model of the sovereign-bank diabolic loop, and establish four results. First, the diabolic loop can be avoided by restricting banks' domestic sovereign exposures relative to their equity. Second, equity requirements can be lowered if banks only hold senior domestic sovereign debt. Third, such requirements shrink even further if banks only hold the senior tranche of an internationally diversified sovereign portfolio--known as ESBies in the euro-area context. Finally, ESBies generate more safe assets than domestic debt tranching alone; and, insofar as the diabolic loop is defused, the junior tranche generated by the securitization is itself risk-free.