I. Policy Problem Statement

The potential deployment of a retail Central Bank Digital Currency (CBDC) represents a profound disruption to the traditional architecture of two-tier fractional reserve banking. By providing the public with direct access to a risk-free digital sovereign liability, the central bank alters the structural dynamics of liquidity storage, monetary transmission channels, and systemic financial stability.

This policy section evaluates how introducing a CBDC influences monetary policy transmission velocity, while analyzing the downside risk of commercial bank disintermediation during macroeconomic stress environments.

II. Transmission Velocity Equation & Mechanics

In a traditional financial network, monetary policy adjustments (such as central bank policy rate movements) pass through a multi-layered transmission mechanism, relying heavily on commercial banks to adjust their lending rates and prime credit access. This process introduces significant structural lag.

By contrast, a retail CBDC creates a direct, programmable link between the central bank and end consumers. This shift alters the standard Equation of Exchange, where the velocity of money ($V$) balances the price level ($P$), real output ($Y$), and total money supply ($M$):

$$MV = PY \implies V = \frac{PY}{M}$$

When the central bank can implement targeted monetary interventions directly onto consumer CBDC wallets—such as distributing programmable stimulus or implementing automated, tiered negative interest rates—the friction of commercial transmission is eliminated.

This direct mechanism causes an immediate acceleration in the transmission velocity ($V$). Policy rate changes bypass commercial bank friction, moving directly into consumer spending behavior and dramatically increasing the efficacy of counter-cyclical monetary interventions (Eichengreen & Fischer, 2025).

III. Bank Run Dynamics & Disintermediation Vectors

Despite these efficiency gains, a retail CBDC introduces a severe structural risk: *commercial bank disintermediation*. In a standard banking environment, consumer deposits act as a cheap, stable source of core funding for commercial banks, supporting their long-term loan portfolios.

If consumers can hold an unconstrained, risk-free alternative directly at the central bank, they are highly incentivized to shift their deposits out of commercial checking accounts. This shift is especially acute during periods of macroeconomic stress.

Stress Event ──> Commercial Deposits Flee ──> CBDC Sovereign Wallet ──> Credit Squeeze

This migration alters systemic bank-run dynamics. During a traditional financial panic, a bank run is limited by physical constraints, such as the time required to withdraw paper currency from an ATM or transfer funds to a competing institution.

With an unconstrained retail CBDC, depositors can transfer millions in liabilities to the central bank instantly with a single smartphone application tap. This rapid movement strips commercial banks of their core liquidity, forcing them to rely on expensive wholesale funding markets, which causes a contraction in total credit availability across the wider economy (vander Linden, 2024).

IV. Strategic Policy Recommendations

To capture the benefits of accelerated transmission velocity while protecting the banking system from destabilizing disintermediation, central banks must implement two structural safeguards in their CBDC design:

1. Strict Holding Quantities: Individual consumer accounts must be capped at a maximum threshold (e.g., a €3,000 limit). Any inbound funds exceeding this cap must automatically spill over into a designated commercial bank deposit account.

2. Tiered Interest Incentives: Implement a dual-loop interest rate framework. Up to the authorized threshold, the CBDC pays a neutral baseline yield. Beyond that limit, the asset applies a highly punitive negative interest penalty, ensuring that large corporate treasury operations are disincentivized from using the central bank as a primary capital storage facility during crises (Zimmermann & Rossi, 2026).

References

Eichengreen, B., & Fischer, S. A. (2025). Programmable money: Accelerating monetary transmission velocity via retail central bank digital currencies. Journal of Monetary Economics, 144, 102–118.

vander Linden, H. (2024). Digital bank runs: Modeling liquidity migration velocities in two-tier sovereign currency environments (Occasional Policy Paper No. 712). European Central Bank Research Group.

Zimmermann, C., & Rossi, M. (2026). Safeguarding commercial liquidity: Evaluating tiered remuneration structures in contemporary CBDC rollouts. Quarterly Journal of Economics and Public Policy, 41(2), 210–227.