Roaming around the econ blogosphere, I often come across what seems to be a sharp divide between those who think monetary policy is all about the manipulation of interest rates and those who think it comes down to varying the quantity of base money. Either side get touchy when the other accuses its favored monetary policy tool, either rates or quantities, of being irrelevant. From my perch, I'll take the middle road between the two camps and say that both are more-or-less right. Either rates, or quantities, or both at the same time, are sufficient instruments of monetary policy. Actual central banks will typically use some combination of rates and quantities to hit their targets, although this hasn't always been the case.
Just to refresh, central banks carry out monetary policy by manipulating the total return that they offer on deposit balances. This return can be broken down into a pecuniary component and a non-pecuniary component. By varying either the pecuniary return, the non-pecuniary return, or both, a central bank is able to create a disequilibrium, as Steve Waldman calls it, which can only be re-equilibrated by a rise or fall in the price level. If the net return on balances is sweetened, banks will flee assets for balances, causing a deflationary fall in prices. If the return is diminished, banks will flock to assets from balances, pushing prices higher and causing inflation.
The pecuniary return on central bank balances is usually provided in the form of a promise to pay interest, or interest on reserves.
The non-pecuniary return, or convenience yield, is a bit more complicated. I've talked about it before. In short, it's sorta like a consumption return. Because central bank balances are useful in settling large payments, and they are rare, banks find it convenient to hold a small quantity of them as a precaution against uncertain events. This unique convenience provided by scarce balances is consumed over time, much like a fire extinguisher's property as a fire-hedge is consumed though never actually mobilized. By increasing or decreasing the quantity of rare balances, a central banker can decrease or increase the value that banks ascribe to this non-pecuniary return.
Now some examples.
The best example of a central bank resorting solely to the quantity tool in order to execute monetary policy is the pre-2008 Federal Reserve. Before 2008, the Fed was not permitted to pay interest on reserves (IOR). This meant that the only return that Fed balances could offer to banks was a non-pecuniary convenience yield, a point that I described here. By adding to or subtracting from the quantity of balances outstanding the Fed could alter their marginal convenience, either rendering them less convenient so as to drive prices up, or more convenient so as to push prices down.
The Bank of Canada is a good example of a central bank that uses both a quantity tool AND an interest rate tool, though not always both at the same time. Since 1991, according to Mark Sadowski, the BoC has paid interest to anyone who holds overnight balances. This is IOR, although in Canada we refer to it as the deposit rate. In addition to paying this pecuniary return, BoC balances also yield a non-pecuniary return. Banks who hold balances enjoy a stream of consumptive returns, or a convenience yield, that stems from both the rarity of BoC balances and their exceptional liquidity.
The best way to "see" how these two returns might be decomposed is by looking at the short term rental market for Bank of Canada balances, or the overnight market. In Canada, this rate is called CORRA, or the Canadian overnight repo rate. A bank will only part with BoC balances overnight if a prospective borrower promises to sufficiently compensate the lending bank for foregone returns. Assuming that the Bank of Canada's deposit rate is 2%, a potential lender will need to be compensated with a pecuniary return of at least 2% in order to dissuade them from socking away balances at the BoC's deposit facility.
The lender will also need to be compensated for doing without the non-pecuniary return on balances. If the overnight lending rate, CORRA, is 2.25%, then we can back out the rate that a lender expects to earn for renting out the non-pecuniary services provided by balances. Since the lender of balances receives the overnight rate of 2.25% from the borrowing bank, and 2% of this can be considered as compensation for foregoing the 2% pecuniary return on balances, that leaves the remaining 0.25% as compensation to the lender for the loss of the non-pecuniary return.
So in our example, the pecuniary and non-pecuniary returns on BoC balances are 2% and 0.25% respectively, for a total return of 2.25%.
The Bank of Canada meets each six weeks, as Nick Rowe points out, upon which it promises to provide banks with a given return on settlement balances, say 2.25%, for the ensuing six week period. When it next meets, the Bank will introduce whatever changes to this return that are considered necessary for it to hit its monetary policy targets. The BoC can modify the return by changing either the pecuniary component of the total return, the non-pecuniary component, or some combination of both.
Say it modifies only the non-pecuniary component while leaving their pecuniary return untouched. For instance, with the overnight rate trading at 2.25%, the BoC might announce that it will conduct some open market purchases in order to increase the quantity of balances outstanding, while keeping the deposit rate fixed at 2%. By rendering balances less rare, purchases effectively reduce the non-pecuniary return on balances. As a reflection of this shrinking return, the overnight rate may fall a few basis point, or it may fall all the way to 2%. Whatever the case, the rate at which banks now expect to be compensated for foregoing the non-pecuniary return on balances has been diminished. Banks will collectively try to flee out of overpriced clearing balances into assets, pushing up the economy's price level until balances once again provide a competitive return. This sort of pure quantity effect is the story that the quantities camp likes to emphasize.
The story told by the quantities camp is exactly how the BoC loosened policy between April 2009 and May 2010. At the time, the BoC injected $3 billion in balances *without* a corresponding decrease in the deposit rate. The overnight rate fell from 0.5% until it rubbed up against the 0.25% deposit rate. The lack of a gap between the overnight rate and the deposit rate indicated that the injection had reduced the overnight non-pecuniary return on balances to 0%. After all, if lenders still expected to be compensated for forgoing the non-pecuniary return on balances, they would have required that the overnight rate be above the deposit rate.
The BoC's decision to reduce the overnight non-pecuniary return on balances to 0% would have generated a hot potato effect as banks sold off lower-yielding BoC balances for higher-yielding assets, thus pushing prices higher. A change in quantities, not rates, was responsible for the April 2009 to May 2010 loosening.
Likewise, in June 2010, the BoC tightened by using quantities, not rates. Open market sales sucked the $3 billion in excess balances back in, thereby increasing the marginal convenience yield on central bank balances. The deposit rate remained moored at 0.25%, but the overnight rate jumped back to 0.5%, indicating that the overnight non-pecuniary return on balances had increased from 0% to 0.25%. This sweetening in the return on balances would have inspired a portfolio adjustment away from low-yielding assets into high-yielding central bank balances, a process that would have continued until asset prices had fallen far enough to render investors indifferent once again along the margin between BoC deposits and assets. Once again quantities, not rates, did all the hard work.
While the BoC chose to tighten in June 2010 by changing quantities, it could just as easily have tightened by changing rates. For instance, if it had increased the deposit rate to 0.5% while keeping quantities constant, then the net return on balances would have risen to 0.5%, the same return that was generated in the last paragraph's quantities-only scenario. This sweetening in the return on balances would have caused the exact same chain of portfolio adjustments and falling asset prices that the quantities-only scenario caused.
Alternatively, the BoC could have tightened through some combination of quantities AND rates. It might have increased the deposit rate from 0.25% to 0.4%, and then conducted just enough open market sales to increase the non-pecuniary return on balances from 0% to 0.1%, for a total combined return of 0.5%. The ensuing adjustments would have been no different than if tightening had been accomplished by quantities-only or rates-only.
Putting aside the period between April 2009 and June 2010, does the Bank of Canada normally execute monetary policy via rates or quantities? A bit of both, I'd say. At the end of a six week period, say that the Bank wishes to tighten. It typically tightens by announcing a 0.25% rise in its target for the overnight rate combined with a simultaneous 0.25% rise in the deposit rate. The overnight rate, or the rental rate on clearing balances, will typically rise immediately by 0.25%, reflecting the sweetened return on balances.
Did rates or quantities do the heavy lifting in pushing up the return on balances? Put differently, was it the threat that open market sales might increase the convenience yield on balances that tightened policy, or was it the improvement in the deposit rate? I'd argue that the immediate punch would have been delivered by the change in the deposit rate. CORRA, the rental rate on balances, jumped because overnight borrowers of BoC balances were suddenly required to compensate lenders for the higher pecuniary rate being offered by the BoC on its deposit facility. Quantities don't enter into the picture at all, at least not at first. The rates-only camps seems to be the winner.
However, as the ensuing six-week period plays out, market forces will push the rental rate on BoC balances (CORRA) above or below the Bank's target, indicating an improvement or diminution of the total return on balances. The BoC has typically avoided any incremental variation of the deposit rate to ensure that the rental rate, or return on balances, stays true to target over the six week period. Rather, it has always used quantity changes (or the threat thereof) to modify the non-pecuniary return on balances during that period, thereby steering the rental rate back towards target. First rates, and then quantities, conspire together to create Canadian monetary policy.
To sum up, the Bank of Canada's monetary policy is achieved, it would seem, through a complex combination of rate and quantity adjustments. The rates vs. quantities dichotomy that sometimes pops up on the blogosphere simplifies what is really a more nuanced story. Monetary policy can certainly be carried out by focusing on quantity adjustments to the exclusion of rate adjustments (as was the case with the pre-2008 Fed) or vice versa . However, modern central banks like the Bank of Canada use rates, quantities, and some combination of both, to achieve their targets.
Note: The elephant in the room is the zero-lower bound. But the zero lower bound needn't prevent rates or quantities from exerting an influence on prices. On the rates side of the equation, the adoption of a cash-penalizing mechanism along the lines of what Miles Kimball advocates would allow a central bank to safely push rates below zero. As for the quantity side of the equation, the threat of Sumnerian permanent increases in the monetary base may not be able to reduce the overnight non-pecuniary return on balances once that rate has hit zero, as Steve Waldman points out... but they can certainly reduce the future non-pecuniary returns provided by balances. Reductions in future non-pecuniary returns should be capable of igniting a hot potato effect, albeit a diminishing one, out of balances and into assets.
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