I’ve written a new paper motivated by my belief that the recent financial crisis was in no small part a failure of economic theory and therefore of economic thinking. In particular, there is a missing model of banking that was well understood a century ago, but is completely unfamiliar to modern scholars and practitioners. The goal of this paper is to introduce modern students of money and banking to the model of money that shaped the 19th century development of a financial infrastructure that both supported modern economic growth for more than 100 years and was passed down to us as our heritage before we in our hubris tore that infrastructure apart.
Another goal is to illustrate what I believe is a fundamental property of environments with (i) liquidity frictions and (ii) a large population with no public visibility but a discount factor greater than zero: in such an environment anyone with a notepad, some arithmetic skills, and some measure of public visibility can offer – and profit from – the account-keeping services that make incentive feasible a much better allocation than autarky for the general populace. Importantly collateral is completely unnecessary in a bank-based payments system.
This model has two key components. First, banks transform non-bank debt into monetary debt. Thus, the transformative function of banking is not principally a matter of maturity, but instead of the nature of the debt itself, that is, of its acceptability as a means of exchange. Second, monetary debt is money (contra Kocherlakota 1998). There is no hierarchy of moneys where some assets have more monetary characteristics than others. Instead there is only monetary debt and non-monetary debt. When we study this very simple model of money in an environment with liquidity frictions using the tools of mechanism design, we see that the economic function of the banking system is to underwrite a payments system based on unsecured debt and thereby to make intertemporal budget constraints enforceable or equivalently to make it possible for the non-banks in our economy to monetize the value of the weight that they place on the future in the form of a discount factor. Banking transforms an autarkic economy into one that flourishes because credit is abundantly available. In this model, constraints on the economy’s capacity to support debt are not determined by “deposits” or by “collateral”, but instead by the incentive constraints associated with banking.
In this environment, banking provides the extraordinary liquidity that is only possible when the payments system is based on unsecured debt. Underlying this form of liquidity is the banks’ profound understanding of the incentive structures faced by non-banks, as it is this understanding that makes it possible for banks to structure the system of monetary debt so that it is to all intents and purposes default-free. (This is actually a fairly accurate description of 19th century British banking. The only people who lost money were the bank owners who guaranteed the payments system. See Sissoko 2014.) Although this concept of price stable liquidity is unfamiliar to many modern scholars, Bengt Holmstrom (2015) has given it a name: money market liquidity. In such a system the distinctions between funding liquidity and market liquidity collapse, because the whole point of the banking system is to ensure that default occurs with negligible probability. Thus, the term money market liquidity references the idea that in money markets, the process by which assets are originated must be close to faultless or instability will be the result, because the relationship between money – when it takes the form of monetary debt – and prices is not inherently stable (cf. Smith 1776, Sargent & Wallace 1982).
This paper employs the tools of New Monetarism, mechanism design, and more particularly the model of Gu, Mattesini, Monnet, and Wright (2013) to explain the extraordinary economic importance of the simplest and most ancient function of a bank: in this paper banks are account-keepers, whose services support a payment system based on unsecured credit. Unsecured credit is incentive feasible, because banks provide account-keeping services and can use the threat of withdrawing access to account-keeping services to make the non-bank budget constraint enforceable.
The basic elements of the argument are this: an environment with anonymity, liquidity frictions and somewhat patient agents is an environment that begs for an innovation that both remedies the problem of anonymity and realizes the value of the unsecured credit that the patience of the agents in the economy supports. I argue that the standard way in which economies from ancient Rome to medieval Europe to modern America address this problem is by introducing banking – or fee-based account-keepers – in order to alleviate the problem of anonymity that prevents agents from realizing the value inherent in the weight they place on the future. I demonstrate that in this environment, the introduction of a bank improves welfare. The improvement in welfare can be dramatic when the discount factor is not close to zero.
This paper uses the environment of Gu, Mattesini, Monnet, and Wright (2013) but is distinguished from that model, because here the focus is on a different aspect of banking. We study how the account-keeping function of banks serves to support unsecured credit, whereas GMMW studies how the deposit-taking function of banks is able to support fully collateralized credit.
The model of banking in this paper has implications that are very different from much of the existing literature on banking. This literature typically assumes the anonymity of agents and then argues – contrary to real-world experience – that unsecured non-bank credit is unimaginable (see, e.g., Gorton & Ordonez 2014, Monnet & Sanches 2015). In other words, the existing literature takes the position that in the presence of anonymity, no paid account-keeper will arise who will make it possible for agents in the economy to realize the value of unsecured credit that their discount factor supports. In the absence of unsecured credit, lending is generally constrained as much by the available collateral or deposits, as by incentive constraints themselves. This paper argues that standard assumptions such as loans must equal deposits (see, e.g. Berentsen, Camera & Waller 2007) or debt must be supported by collateral (see e.g. Gu, Mattesini, Monnet, and Wright (2013), Gorton & Ordonez 2014) are properly viewed as ad hoc assumptions that should be justified by some explanation for why banking has not arisen and made unsecured credit available to anonymous agents.
 While Holmstrom (2015) and this paper agree on the principle that money market liquidity is characterized by price stability, the mechanism by which that price stability is achieved is very different in the two papers: for Holmstrom it is the opacity of collateral that makes price stability possible.