The previous module took the policy rate as given and asked how it reaches the economy. This module asks the prior, mechanical question: how does the central bank actually make the policy rate happen? Announcing a rate is not the same as achieving it. The operating framework is the plumbing — the facilities and operations through which the bank steers the actual cost of overnight money to its chosen target. It is technical, and it is where many developing-country monetary frameworks quietly fail.
The operational target
A central bank cannot directly set the lending rates faced by firms; it can only control the very short end — the overnight interest rate at which banks lend reserves to each other (the interbank rate). This is the operational target. The whole framework is designed to keep that overnight interbank rate close to the policy rate, on the logic that the rest of the yield curve and the transmission channels build outward from it. Everything else — the corridor, open-market operations, reserve requirements — is in service of steering this one rate.
The interest-rate corridor
How standing facilities bound the rate
The central bank offers two standing facilities, available to banks on demand, that form a corridor around the policy rate: • A lending facility (at the top) — banks can always borrow reserves overnight from the central bank at a rate above the policy rate. No bank will pay more than this in the interbank market, so it caps the overnight rate. • A deposit facility (at the bottom) — banks can always park reserves at the central bank overnight at a rate below the policy rate. No bank will lend for less than this, so it floors the overnight rate. The interbank rate is thus penned between the floor and the ceiling, and the central bank steers it toward the policy rate (typically the corridor's midpoint) by managing the quantity of reserves in the system through open-market operations. A narrow corridor keeps the rate tightly anchored; a wide one lets it drift. The corridor is the skeleton of a modern operating framework.
Open-market operations
Within the corridor, the central bank fine-tunes by changing the supply of reserves through open-market operations (OMO): buying securities or lending via repos injects reserves (pushing the overnight rate down); selling securities or issuing its own bills (reverse repos) withdraws reserves (pushing it up). The bank forecasts the 'autonomous' factors that move reserves (currency demand, government cash flows) and conducts OMO to offset them and keep the system's reserves at the level consistent with the target rate. Good liquidity forecasting is the unglamorous core competence of a central bank's operations desk — get it wrong and the overnight rate jumps around regardless of the announced policy rate.
Reserve requirements
Reserve requirements (a cash reserve ratio — banks must hold a fraction of deposits as reserves at the central bank) play a supporting role. Originally a monetary-control tool, in modern frameworks they mainly serve to create a stable, predictable demand for reserves (which makes the overnight rate easier to steer) and as a liquidity buffer. Averaging provisions (banks must meet the requirement on average over a maintenance period, not every day) give banks flexibility that smooths the overnight rate. In some developing economies reserve requirements are still used more actively as a blunt instrument to absorb structural excess liquidity.
When the plumbing fails
A thin or segmented interbank market
The whole framework rests on a functioning interbank market — banks lending reserves to one another so that the central bank's steering of aggregate reserves translates into one market-clearing overnight rate. In many developing economies that market is thin and segmented: a few large banks are structurally long on liquidity and a tail of smaller banks are short, but counterparty-risk concerns, collateral shortages, and market-power frictions stop them trading freely. The result: surplus liquidity piles up at the big banks while small banks are starved, the overnight rate is volatile and disconnected from the policy rate, and the central bank's signal is lost at the very first step. This is why African operating frameworks often feature large, persistent OMO to mop up structural excess liquidity, and why building a deep, trusted interbank market is a precondition for monetary policy to work — the operational counterpart to the weak-transmission problem of the last module. A central bank that cannot reliably hit its own operational target cannot expect the rest of the transmission chain to carry its policy.
Exercise
A central bank announces a policy rate of 9%, but the overnight interbank rate swings between 5% and 13% week to week, and a few large banks sit on huge excess reserves while small banks frequently scramble for funds. (1) Explain what an interest-rate corridor is and how it should be keeping the overnight rate near 9%. (2) Diagnose why the rate is swinging so widely despite the announced policy rate. (3) Explain the role of liquidity forecasting and open-market operations in fixing the volatility. (4) Why does the segmentation between liquidity-rich and liquidity-poor banks undermine the whole framework, and what would address it?