This column explores the implications of such a venture by central banks using a classic banking model. 有足够的竞争, a central bank digital currency can be beneficial and achieve the optimal allocation of funds. 然而, it also risks giving central banks excessive monopoly power, 哪些会导致较差的结果.

本专栏是VoxEU辩论的主要评论 数字货币的未来.

Recent advances in cryptographic and distributed ledger techniques (von zur Gathen 2015, Narayanan等人. 2016) have opened the door to the widespread use of digital currencies. 而像比特币这样的私人项目, Ethereum, and Libra have led the introduction of these currencies, researchers and policymakers have explored the possibility that central banks could also issue digital currencies, 中央银行数字货币(CBDC), 并向公众开放. Cecchetti and Schoenholtz (2018) and Niepelt (2020) offer concise yet informative summaries of many of the economic, 法律, and technological issues related to the adoption of a CBDC.

CBDCs may be token-based or account-based (see 国际清算银行 2018). 在基于令牌的系统中, the validity of the payment object has to be verified and transactions can be anonymous. In an account-based system, the account holder needs to be verified. Each system has its own advantages and disadvantages over the other. 在我们的论文中(Fernández-Villaverde等人). 2020), we examine the account-based version of a CBDC, i.e. a world where citizens hold direct deposit accounts at the central bank.1有了这样的设置, the central bank will be thrown into competition with commercial banks for deposits, and thus will need to confront a key function of the banking system: intermediating between savers and investors and maturity transformation. Many defenders of CBDCs see this development as one key advantage of this new type of money, 自, 他们认为, a central bank open to all will limit future financial crises, 银行挤兑, 和救助. 然而, this feature also raises a whole range of intricate and important questions.

What effects will the introduction of a CBDC and the opening of central bank facilities have on financial intermediation? Will a CBDC impair the role of the financial system in allocating funds to productive projects? Or can we reorganise the financial system in such a way that a CBDC will still allow the right flow of funds between savers and investors? Will a CBDC make 银行挤兑 disappear and stabilise the financial system?

在最近的一篇论文中(Fernández-Villaverde等人). 2020年)，我们试图回答这些问题. 我们的调查是基于这样的假设, 与商业银行相比, a central bank is not skilled in identifying the best investment projects that yield the highest net present value in the market. This lack of skill might be due to the central bank not having a good technology to screen, 监控, 清算生产性项目. It might also be due to the presence of political-economic considerations that limit the central bank’s abilities to select superior investment projects.

We embed this idea in a version of the classic model of banking by Diamond and Dybvig (1983), 中央银行的存在增强了这一点. We select the Diamond-Dybvig model because it is a workhorse of modern banking theory and it emphasises the role of banks in maturity transformation. 特别是, banks finance long-term projects with demand deposits that may be withdrawn at a shorter horizon. Diamond and Dybvig have shown that the banking system can achieve the first-best, effectively providing optimal insurance against the liquidity needs of depositors, 但银行挤兑也可能出现. Their framework is thus particularly suitable to understanding how a CBDC affects the scope of a financial crisis.

在我们的框架中, the CBDC takes the form of the public having demand deposit accounts at the central bank. 就像商业银行一样, the central bank holds assets to fund these liabilities, 但是我们假设, 与商业银行不同, the central bank cannot invest in long-term projects itself. The central bank instead will need to rely on investment banks and their expertise to invest in these projects by providing them with non-callable wholesale loans. 为了我们的分析和, 最终, 作为思考这些问题的起点, we assume that this delegation works without friction: relying on investment banks is just as good for the central bank as having the expertise to invest in these long-term projects on its own, 只要这些存款不需要被收回.

Our first main result is an interesting equivalence result that the set of allocations achieved with private financial intermediation (i.e. the first-best allocation) can also be achieved with a CBDC, 前提是允许与商业银行竞争.

This equivalence result might seem to vindicate the views of proponents of a CBDC: the socially optimal amount of maturity transformation can likewise be produced in an economy where the central bank has been opened to all. 但是我们的等效结果有一个险恶的对应. If the competition from commercial banks is impaired (for example, through some fiscal subsidisation of central bank deposits or by changes in the structure of possible 银行挤兑), the central bank has to be careful in its choices to avoid creating havoc with maturity transformation. These insights echo similar concerns raised by Cecchetti and Schoenholtz (2018).

While the central bank is capable of offering the socially optimal deposit contract just as much as commercial banks are, we demonstrate that the rigidity of the central bank's contract with the investment banks leads to different allocations during banking panics. We have assumed that the loan of the central bank to the investment bank is not callable: this assumption now plays a crucial role. It implies that the central bank's indirect investment in the long asset is protected from early liquidation. 我们展示了这个, 反过来, either completely deters runs on the central bank or makes runs on the central bank less likely than runs on the commercial banking sector. Depositors internalise this feature and will choose to exclusively deposit with the central bank. 这是, due to the commitment aspect of the rigid contract between the central bank and the investment banks, the central bank becomes the monopoly provider of deposits.

垄断通常会产生一系列新的令人头疼的问题, and this monopoly of a central bank is no exception in that regard. The monopoly power of the central bank can endanger the supply of the first-best amount of maturity transformation in the economy by allowing the central bank to deviate from offering the socially optimal deposit contract, 最终 making depositors worse off as a consequence.

Our results can be compared with other recent studies in the literature that have highlighted different aspects of the potential benefits and risks of a CBDC. 例如, Brunnermeier and Niepelt (2019) have provided conditions under which the introduction of a CBDC has no effect on the equilibrium allocation. Their analysis assumes that the central bank and private-sector financial institutions are equally adept at identifying investment opportunities and 监控ing loans, assumptions that we find are unlikely to hold in the real world. 另外, their framework does not account for the kind of maturity transformation that characterises the essence of the banking business: the acquisition of long-term illiquid assets financed by short-term liabilities. Other studies, including Andolfatto (2018) and 赵 et al. (2019), have emphasised the presence of market power in the banking system when considering the issuance of a CBDC. These authors find that an interest-bearing CBDC can lead to a shift of funds out of bank deposits and into the digital currency, which causes a decline in deposits and bank-funded investment. These conclusions crucially depend on a sufficiently concentrated banking system, and maturity transformation is absent in their analysis. 威廉姆森(2019)认为, 通过发行有息的CBDC, the central bank can economise on scarce safe collateral, 哪些对社会有益, even though its implementation might undermine central bank independence.

Given our results and the comparison with the existing literature, we conclude that a CBDC and the associated central bank open to all is indeed capable of delivering the socially optimal amount of maturity transformation, 流动性保险, 减少银行挤兑. 然而, it also gives an unseen power to central banks. It is not unreasonable to be concerned about the abuse of such power.

Authors' note: The views expressed in this column are those of the authors and do not necessarily reflect those of the Federal Reserve System or the 费城联邦储备银行.

参考文献

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赵, J, M Davoodalhosseini, J江, (2019), “央行数字货币和银行业务,加拿大银行工作人员工作文件2019-20, 五月.

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Narayanan, A, J Bonneau, E Felten, A Miller, and S Goldfeder (2016), 比特币和加密货币技术，普林斯顿:普林斯顿大学出版社.

Niepelt, D(2020)，”Digital money and central bank digital currency: An executive summary for policymakers”VoxEU.2月3日.

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威廉姆森, S (2019), “Central bank digital currency: Welfare and policy implications,工作论文:西安大略大学.

尾注

¹ Most CBDC proposals are structured around the idea of a “central bank granting universal, 电子, 24x7, national-currency-denominated and interest-bearing access to its balance sheet” (Barrdear and Kumhof 2016, p. 7).