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We study the macroeconomic implications of time-varying precautionary savings within a general equilibrium model with borrowing constraints, aggregate shocks and uninsurable idiosyncratic unemployment risk. Our framework generates limited cross-sectional household heterogeneity as an equilibrium outcome, thereby making it possible to analyse the role of precautionary saving over the business cycle in an analytically tractable way. The time-series behaviour of aggregate consumption generated by our model is closer to the data than that implied by the hand-to-mouth and representative-agent models, and it is comparable to that produced by the Krusell and Smith (1998) model.

The purpose of this text is to show that the distinction between optimality and sustainability leads to the identification of a new paradox for the management of public debts, which is called the pseudo-paradox of Triffin. It is based on three observations. First, the status of safe assets or international store of value allows low real financing costs for the public debts of developed countries, even with inflation now high. Then, the international increase in demand for safe assets over the past twenty years has led to an increase in public debt to benefit from low interest rates in the face of new spending. Finally, the return of macroeconomic shocks can suddenly cause the status of safe assets to be lost. The paradox is based on the increase in optimal short-term debt and the decrease in sustainable long-term debt. We present this paradox and develop the implications for the European framework.Classification JEL: H50, H54, H60, H62, H63, H68.

This paper derives the optimal money injection at the Zero Lower Bound (ZLB), in a tractable model where households hold heterogeneous money holdings due to explicit financial frictions, such as limited participation and temporary binding credit constraints. This framework is motivated by recent empirical findings. A deleveraging shock generates deflationary pressure and a fall in the real interest rate, pushing the economy to the ZLB. The main result is that open-market operations can stabilize the economy at the ZLB whereas lump-sum money transfers cannot. Moreover, an optimal money injection does not avoid the economy being at the ZLB.

We present a truncation theory of idiosyncratic histories for heterogeneous-agent models. This method allows us to solve for optimal Ramsey policies in such models with aggregate shocks. The method can be applied to a large variety of settings, with occasionally binding credit constraints. We use this theory to characterize the optimal level of unemployment insurance over the business cycle in a production economy. We find that the optimal policy is countercyclical.

Of the many good ideas currently being discussed in Europe, the most interesting proposal is to let national unemployment schemes manage the regular business cycle, and to provide European financing to extend the duration of unemployment benefits during a crisis period.

This paper analyses the effects of money shocks on macroeconomic aggregates in a tractable flexible-price, incomplete-markets environment that generates persistent wealth inequalities amongst agents. In this framework, current inflation redistribute wealth from the cash-rich employed to the cash-poor unemployed and induce the former to increase their labour supply in order to maintain their desired levels of consumption and precautionary savings. If the shocks are persistent, however, they also raise inflation expectations and thus deter the employed from saving and supplying labour. We relate the strength of these two inflation taxes to the underlying parameters of the model and study how they compete in determining the overall sign and slope of the implied ‘output-inflation tradeoff' relation.

A liquidity-insurance motive for monetary policy operates when heterogeneous households use government-provided liquidity (\"money\") to insure idiosyncratic risk. In our tractable sticky-price model this changes the central bank's trade-off by adding a linear benefit of insurance in the second-order approximation to aggregate welfare. Inflation volatility hinders the consumption volatility of constrained households as a side-effect of liquidity-insuring them; but price stability has quantitatively significant welfare costs only when monopolistic rents are also large, which indicates a complementarity between imperfect-insurance and New-Keynesian distortions. Helicopter drops are welfare-superior to open-market operations to achieve insurance, but quantitatively their benefit is surprisingly small.

The uncertainty about growth, the return of inflation and the need for an energy transition are renewing the economic policy debate. If the situation was previously referred to as secular stagnation, other names are emerging: stagflation reflation. Beyond the diagnosis, what use should be made of monetary or fiscal policy in an environment of high debt ? This issue is all the more important as the European rules of budgetary coordination are being questioned. Based on concrete examples, this article asserts the central role of fiscal policy in relation to monetary policy. This development should be understood as a rehabilitation of “functional finance” in a measured form. The implications for the mandate of central banks and the European fiscal framework are developed.

We analyse the effects of fiscal expansions when public debt is used as liquidity by the private sector. Aggregate shocks are introduced into an incomplete-market economy where heterogenous agents face occasionally binding borrowing constraints and store wealth to smooth out idiosyncratic income fluctuations. Debt-financed increases in spending facilitate self-insurance by bond holders and may crowd in private consumption. They also loosen the borrowing constraints faced by firms, thereby raising labour demand and possibly the real wage. Whether private consumption and wages rise or fall ultimately depends on the relative strengths of the liquidity and wealth effects that arise following the shock.

The main paradigm in macroeconomics is shifting towards heterogeneous agents models, which are able to account for inequalities and financial imperfections. This evolution comes from new policy questions after the financial crisis, but also from the availability of individual data, which allows a better connection between theories and data. Within these models, financial markets are incomplete and a concept of liquidity naturally arises. This article presents the recent results in this dynamic literature, as the analysis of the inequalities in the United States, the need for a world liquidity, the effect of the public debt on asset prices, or the extent of precautionary saving of households. JEL Codes: E21, E44, D91, D31.