Sovereign Grassroots Currencies: A CBDC Architecture for Credit and Monetary Policy (Full Version)
Organizations: London School of Economics, UK · Weizmann Institute of Science, Israel
Abstract
A Central Bank Digital Currency (CBDC) is central-bank money in digital form, held by the public. Leading designs have two limitations: conversion from bank deposits into CBDC can accelerate deposit flight, requiring safeguards, and the CBDC stays outside credit creation and monetary-policy operations. Here we present a CBDC architecture based on grassroots currencies that overcomes these limitations. The architecture has three components: (1) Money: sovereign grassroots coins, which are digital debts of one unit of fiat currency issued by the central bank, constituting a direct CBDC; (2) Credit and Liquidity: non-sovereign grassroots coins, which are digital debts of one unit of the same fiat currency, redeemable at par, that can be issued by any person, natural or legal, thus adding credit; and (3) Interest: grassroots bonds, sovereign and non-sovereign, adding maturity and thus interest, standard banking instruments, and the central bank's instruments of monetary policy. The central bank can therefore lend, absorb liquidity, set its rates and buy and sell securities in the coins and bonds the public holds, choosing the counterparties and terms of its credit operations, and without converting bank deposits into newly issued central bank money on demand. We prove that the arbitrage-free price of any non-sovereign grassroots coin whose issuer redeems it on demand is one unit of the fiat currency. The central bank can choose to deal with any counterparty, not just banks, and we argue that the central bank's interest rates on lending and bonds bound from above and below the corresponding interest rates of its counterparties. Sovereign and non-sovereign grassroots coins and bonds have been implemented and tested on a small scale.
Figures & tables
| Requirement [ 12 ] | How sovereign grassroots coins meet it | Status |
|---|---|---|
| 1. Foundational principles | ||
| 1.a Do no harm: disintermediation | No retail account, and no conversion of a bank deposit on demand [ 64 ] : the central bank issues its coins in exchange for fiat coins and by its own payments, so no deposit becomes newly issued central bank money; with the credit component it issues them by mutual credit lines (Section 4 ) | argued |
| 1.b Do no harm: runs | The central bank can always fulfil a presentation of its own coins by issuing a fiat coin, and what the public can obtain of them by redemption is bounded by what it has issued, so there is no open-ended digital run into central bank money | argued |
| 1.c Do no harm: monetary policy | The coins bear no interest, as cash does not, so they introduce no interest-rate competition with deposits, and policy is conducted as it is today; with the bonds the policy rate becomes the rate at which the central bank lends its coins (Section 5 ) | argued |
| 1.d Coexistence | Redeemable at face value for a unit of the fiat currency by the central bank’s obligation (obligation 3); cash and bank money continue; the central bank joins a non-sovereign grassroots currency already in operation as one more issuer | by construction |
| 1.e Innovation and efficiency | A payment needs no infrastructure beyond the parties’ devices and the machines holding the issuer’s log; every person may issue a currency of their own beside the central bank’s (Section 4 ) | by construction |
| Requirement [ 12 ] | How sovereign grassroots coins meet it | Status |
|---|---|---|
| 2. Instrument features | ||
| 2.a Convertible at par | Redeemable by the central bank for one unit of the fiat currency, which it issues (obligation 3) | by construction |
| 2.b Convenient | A payment is a signed message countersigned by the central bank, on the parties’ own devices; no account beyond a keypair; ease of use unmeasured | specified |
| 2.c Accepted and available, offline included | Acceptance by the central bank is enforced by the contract; a payment needs the payer, the payee, the central bank and the machines holding its log, so it proceeds over any network that reaches them, and not offline from the central bank | not met |
| 2.d Low or no cost to end users | No intermediary, so no fee is required by the architecture; what a person pays is the cost of operating their device, and what an issuer charges for its services, neither measured | by construction; cost unmeasured |
| 3. System features | ||
Appendix figures & tables1 asset
Supplementary material from the paper’s appendix.
Appendix
| Party | Holdings after the run |
|---|---|
| Central bank | 17 cb-coins, 10 diana-coins |
| Alice | 5 bob-coins, 15 charlie-coins, 8 alice-coins, 4 frank-coins |
| Bob | 10 alice-coins, 18 diana-coins, 5 cb-coins |
| Charlie | 10 alice-coins, 10 eve-coins, 6 charlie-coins |
| Diana | 7 cb-coins, 11 diana-coins, 1 frank-coin, |
| 24 bob-bonds maturing on day 25, 12 frank-bonds maturing on day 28 |