We motivate and provide an overview to New Monetarist Economics. We then briefly describe the individual contributions to the Macroeconomics Dynamics special issues on money, credit, and liquidity.

We study counterfeiting of currency in a search-theoretic model of monetary exchange. In contrast to Nosal and Wallace [Journal of Monetary Economics 54, 229–246 (2007)], we establish that counterfeiting does not pose a threat to the existence of a monetary equilibrium; i.e., a monetary equilibrium exists irrespective of the cost of producing counterfeits, or the ease with which genuine money can be authenticated. However, the possibility of counterfeiting fiat money can affect its value, velocity, output, and welfare, even if no counterfeiting occurs in equilibrium. We provide two extensions of the model under which the threat of counterfeiting can materialize: counterfeits can circulate across periods, and sellers set terms of trade in some matches. Policies that make the currency more costly to counterfeit or easier to recognize raise the value of money and society's welfare, but the latter policy does not always decrease counterfeiting.

This paper presents an integrated theory of money and dynamic credit. I study financial intermediation when both the intermediary and individuals have private information. I show that money is essential to solving two-sided incentive problems under the dynamic credit arrangement. First, requiring settlement with money can induce market trades that generate information-revealing prices to discipline the intermediary. Second, it is optimal for the intermediary to issue money that can record its own history of being used in settlements, and to require that settlements be made with only money that has been returned to the intermediary every settlement period. This arrangement effectively reduces individuals' incentives to deviate and allows intermediation to achieve efficient allocations.

Contemporaries and economic historians have noted several features of medieval and early modern European monetary systems that are hard to analyze using models of centralized exchange. For example, contemporaries complained of recurrent shortages of small change and argued that an abundance/dearth of money had real effects on exchange, especially for the poor. To confront these facts, we build a random-matching monetary model with two indivisible coins with different intrinsic values. The model shows that small change shortages can exist, in the sense that adding small coins to an economy with only large coins is welfare-improving. This effect is amplified by increases in trading opportunities. Further, changes in the quantity of monetary metals affect the real economy and the amount of exchange as well as the optimal denomination size. Finally, the model shows that replacing full-bodied small coins with tokens is not necessarily welfare-improving.

This paper develops a search-theoretic model to study the interaction between banking and monetary policy and how this interaction affects allocation and welfare. Regarding how banking affects the welfare costs of inflation, we find that, with banking, inflation generates lower welfare costs. We also find that lowering inflation improves welfare not just by reducing consumption/production distortions, but also by avoiding financial intermediation costs. Therefore, understanding the nature of financial intermediation is critical for accurately assessing the welfare gain from lowering the inflation rate. Regarding how monetary policy affects the welfare effects of banking, we find that, when the inflation is low, banking is not active in channeling liquidity; when inflation is high, banking is active and improves welfare; and when inflation is moderate, banking is active but reduces welfare. Owing to general-equilibrium feedback, banking is supported in equilibrium even though welfare is higher without banking.

We study a competitive dynamic financial market subject to a transient selling pressure when market makers face a capacity constraint on their number of trades per unit of time with outside investors. We show that profit-maximizing market makers provide liquidity in order to manage their trading capacity constraint optimally over time: they use slack trading capacity early to accumulate assets when the selling pressure is strong in order to relax their trading capacity constraint and sell to buyers more quickly when the selling pressure subsides. When the trading capacity constraint binds, the bid–ask spread is strictly positive, widening and narrowing as market makers build up and unwind their inventories. Because the equilibrium asset allocation is constrained Pareto-optimal, the time variations in bid–ask spread are not a symptom of inefficient liquidity provision.

We compare two stylized frameworks for the implementation of monetary policy. The first framework relies only on standing facilities, whereas the second framework relies only on open-market operations. We show that the Friedman rule cannot be implemented when the central bank uses standing facilities only. For a given rate of inflation, we show that standing facilities unambiguously achieve higher welfare than just conducting open-market operations. We conclude that elements of both frameworks should be combined. Also, our results suggest that any monetary policy implementation framework should remunerate both required and excess reserves.