Reuters reported yesterday that the ECB was considering raising the amount of reserves banks are required to hold at the ECB on average – not immediately, but potentially in autumn. Crucially, this Minimum Reserve Requirement (MRR) is not remunerated, unlike reserves parked at the deposit facility, which currently earns banks 2.25% in interest. Doubling the MRR is estimated to save the ECB close to €4bn annually, and more if interest rates were to be increased further. [...]