货币的数字化（英文版）.pdf

BIS Working Papers No 941 The digitalization of money by Markus K Brunnermeier, Harold James and Jean-Pierre Landau Monetary and Economic Department May 2021 Keywords: digital money, digital currency area, digital dollarization, currency competition. BIS Working Papers are written by members of the Monetary and Economic Department of the Bank for International Settlements, and from time to time by other economists, and are published by the Bank. The papers are on subjects of topical interest and are technical in character. The views expressed in them are those of their authors and not necessarily the views of the BIS. This publication is available on the BIS website (bis). Bank for International Settlements 2021. All rights reserved. Brief excerpts may be reproduced or translated provided the source is stated. ISSN 1020-0959 (print) ISSN 1682-7678 (online) The Digitalization of Money Markus K. Brunnermeier Princeton University Harold James Princeton University Jean-Pierre Landau Sciences Po October 2020 Abstract The ongoing digital revolution may lead to a radical departure from the tradi- tional model of monetary exchange. We may see an unbundling of the separate roles of money, creating fiercer competition among specialized currencies. On the other hand, digital currencies associated with large platform ecosystems may lead to a re-bundling of money in which payment services are packaged with an array of data services, encouraging differentiation but discouraging interoperability between platforms. Digital currencies may also cause an upheaval of the international mon- etary system: countries that are socially or digitally integrated with their neighbors may face digital dollarization, and the prevalence of systemically important platforms could lead to the emergence of digital currency areas that transcend national borders. Central bank digital currency (CBDC) ensures that public money remains a relevant unit of account. Keywords: Digital Money, Digital Currency Area, Digital Dollarization, Currency Compe- tition Contact: markusprinceton.edu. We are grateful to Joseph Abadi for his numerous contributions to this project and to Dirk Niepelt and Johnathan Payne for helpful suggestions. 1 1 Introduction Digitalization has revolutionized money and payments systems. Although digital money itself is not new to modern economies, digital currencies now facilitate instantaneous peer-to-peer transfers of value in a way that was previously impossible. New currencies will emerge as the central lynchpins of large, systemically important social and economic platforms that transcend national borders, redefining the ways in which payments and users data interact. The advent of these new monies could reshape the nature of cur- rency competition, the architecture of the international monetary system, and the role of government-issued public money. Digital money has already surfaced in a variety of contexts. WeChats and Alipays digital wallets have come to dominate the payments system in China. In Africa, mobile providers have launched successful money transfer services, such as Safaricoms M-Pesa. Facebook has led the development of digital currencies for social media networks, an- nouncing plans to issue its own currency, the Libra, which is a type of “stable coin” that will be pegged to a basket of official currencies. Finally, in recent years, thousands of fiat cryptocurrencies maintained on blockchains by anonymous record-keepers have been launched. This paper discusses the key questions and economic implications of digital curren- cies. The first important economic insight is that digital currencies feature innovations that will unbundle the functions served by money (store of value, medium of exchange, and unit of account), rendering the competition among currencies much fiercer. Digital currencies may specialize to certain roles and compete exclusively as exchange media or exclusively as stores of value. The second prediction is that digital money issuers will try to “product differentiate” their currency by re-bundling monetary functions with traditionally separate functions, such as data gathering and social networking services. Both convertibility between digital currencies and interoperability of platforms may be required to maximally exploit the benefits of this type of competition. The importance of digital connectedness, which often supersedes the importance of macroeconomic links, will lead to the establishment of “Digital Currency Areas” (DCAs) linking the currency to usership of a particular digital network rather than to a specific country. The international character of these digital currencies will make both emerging and advanced economies vulnerable to “digital dollarization,” in which the national currency is supplanted by a digital platforms currency rather than another developed countrys currency. Third, digital currency, and its integration with pervasive platforms and services, raises impor- 2 tant questions regarding the competition between private and public money. In a digital economy, cash may effectively disappear, and payments may center around social and economic platforms rather than banks credit provision, weakening the traditional trans- mission channels of monetary policy. Governments may need to offer central bank digital currency (CBDC) in order to retain monetary independence. 2 Monetary Systems and Independent Currencies In order to understand the significance of digital currencies, we first describe the design of traditional monetary systems. We then define what constitutes an independent currency and discuss how digital currencies fit into the traditional paradigm. 2.1 The architecture of monetary systems Traditionally, monetary systems have been organized around an anchor. Any payment instrument in the monetary system is ultimately linked to a fixed amount of the anchor. The anchor can take many forms, such as a commodity or a fiat currency.1 For instance, under the gold standard, the anchor was gold: each unit of currency issued by a gov- ernment was convertible into a unit of gold. In fact, this anchor held together the entire international monetary system under Bretton-Woods, when the U.S. dollar had a legal convertibility into gold and all other currencies were pegged to the dollar. Currently, the anchor in most monetary systems is a government-issued fiat currency. Issuers of money may offer full and unconditional convertibility, or they may instead back the money with other assets without offering full convertibility. Under a convert- ibility arrangement, the issuer of a monetary instrument (which may or may not be an independent currency) makes a legally binding commitment to exchange that instrument at a fixed rate for another payment instrument. Convertibility serves two purposes. First, it serves to maintain the value of the currency. The issuer of a convertible currency ef- fectively ties its hands. It must either fully back its issuance with reserves of another payment instrument or risk forfeiting a claim to its assets if it defaults on its promise to maintain convertibility. Second, convertibility effectively allows one payment instru- ment to replicate the store of value and unit of account properties of another. A system 1 In fact, in the early modern world, many cities and countries had systems with parallel gold and silver currencies, meaning those monetary systems had two anchors. 3 of convertibility among several different types of money creates uniformity among them, typically referred to as the “uniformity of money”. The archetypal example of an issuer that makes a legally binding commitment to convertibility is a bank. Bank deposits are convertible to an equal quantity of the corresponding government-issued fiat currency. If the bank defaults on its obligations, the deposits it issues cease to circulate and deposit holders receive a claim on banks illiquid assets. Backing, on the other hand, also supports the value of a monetary instrument, but it allows the issuer a much greater degree of freedom. An issuer that backs its money with a collection of assets does not always offer full convertibility to those assets. Even if the issuer targets an exchange rate against another currency, it may abandon its target and does not forfeit claims on its assets when doing so. Rather, the issuer manages the value of its money at its own discretion by issuing or buying back money in exchange for those assets. Good examples of backing arrangements are currency pegs and currency bands. Another example is a cryptocurrency “stable coin” that expands and contracts the money supply in order to keep its value fixed relative to that of an official currency, such as the Tether currency (which is “pegged” to the dollar). In each case, the issuer may find it desirable to manage the exchange rate, but it does not face legal consequences for deviating from its initial plan. A related distinction is that between inside and outside money. Inside money repre- sents a claim on a (private) issuing entity. It is a liability on the issuers balance sheet and is in zero net supply. If the issuer of inside money fails to meet the terms of that claim, which typically involve convertibility on demand to some other monetary instrument, the holders of inside money receive a residual claim on the issuers assets. Bank deposits and many forms of e-money, such as Alipays token, are inside money. Outside money, by contrast, is not a claim on anything. Outside money does not appear as a liability on any private entitys balance sheet and is in positive net supply. Nevertheless, outside money may be backed by another type of money. Government-issued fiat currencies, for exam- ple, are outside money regardless of whether they are pegged to some other currency. Similarly, both backed and unbacked cryptocurrencies are outside money. Finally, money comes in multiple forms. There are two main forms of money: account- based money and token money. The key difference between the two types of money lies in the verification process for payments.2 In an account-based system, what must be verified 2 Our characterization of this distinction is taken from Kahn and Wong (2019), who explain it in greater detail. 4 is the payers identity. As such, bank deposits are account-based money: a payment from an account is considered valid if the bank is able to confirm that the person making that payment is the account holder. If it is later discovered that the bank incorrectly identified the payer, the bank assumes liability and refunds the account holder. In a token system, what must be verified is instead the authenticity of the item to be exchanged. Cash and coins are types of token money that have existed for centuries. In a cash transaction, the payee will accept payment only if she believes the cash is genuine, meaning the payee effectively assumes liability if the cash is counterfeit. Modern e-money and cryptocur- rencies are also token money. For example, to transact currency on Alipays network, all that is needed is a password linked to a particular digital “wallet.” No one is required to verify that the person who presented the password is the wallets true owner. Similarly, to transact cryptocurrency, the payer must sign transactions with a “private key” linked to a particular set of coins, but the transaction is valid regardless of who presents that key. Importantly, account-based money tends to be inside money linked to the creation of credit, whereas token money is typically unrelated to the provision of credit. Hence, an expansion in the supply of account-based money may have quite different implications from an expansion in the supply of token money. 2.2 What defines an independent currency? In order to understand what constitutes an independent currency, we first define what it means for a payment instrument to belong to a currency. We say a collection of payment instruments form an independent currency if the following two conditions hold: (i) The payment instruments are denominated in the same unit of account. (ii) Each payment instrument within the currency is convertible into any other. We adopt this definition of an independent currency to ensure that monetary instruments are linked to a currency via their unit of account rather than their properties as exchange media. Hence cash, reserves, and bank deposits denominated in an official currency, for example, are all part of the same currency despite having strikingly different technologi- cal features. If a payment instrument is not part of an existing currency, then it is an independent currency. By this definition, a currency board arrangement like the Hong Kong dollar constitutes a currency independent of the U.S. dollar, as it is denominated in its own 5 unit of account and the peg maintained by the central bank is not legally binding. Bank deposits denominated in dollars are not an independent currency because the convert- ibility arrangement is legally enforceable. In other words, one factor that distinguishes independent currencies is the issuers level of commitment. The issuer of an independent currency denominated in an existing unit of account ultimately retains the option to break any convertibility commitments it has made in the past. Issuers of payment instruments that are not independent currencies forfeit residual claims on their assets if they break their promises. An example that illustrates how several currencies could merge into one is that of the transition from the European Exchange Rate Mechanism (ERM) to the Euro. During this transition period, countries could have decided to break away from the arrangement without forfeiting the ability to issue money. After the Euro was introduced, though, countries did forfeit their ability to issue money, and the multiple currencies ceased to be independent. This definition suggests that several ubiquitous forms of digital money are, in fact, independent currencies. For example, the basket underlying Facebooks Libra currency would consist of many official currencies, so Libra would be denominated in its own unit of account and thus be independent. Fiat cryptocurrencies are clearly independent currencies, as they are not convertible into anything and have their own unit of account. This includes all of the most popular cryptocurrencies, such as Bitcoin and Ether. Even some stable coins, which are backed by a bank account owned by the issuing entity, are independent currencies, because they could continue to exist on an exchange even after the issuer unilaterally abandons the currencys backing. Other types of digital money are not fully independent currencies but nevertheless enable transfers of value that were not previously possible. For instance, many mobile applications now permit peer-to-peer digital transfers, whereas digital transfers under the traditional banking system were typically limit