What does a central bank actually do?

Aug 26 JDN 2458357

Though central banks are a cornerstone of the modern financial system, I don’t think most people have a clear understanding of how they actually function. (I think this may be by design; there are many ways we could make central banking more transparent, but policymakers seem reluctant to show their hand.)

I’ve even seen famous economists make really severe errors in their understanding of monetary policy, as John Taylor did when he characterized low-interest-rate policy as a “price ceiling”.

Central banks “print money” and “set interest rates”. But how exactly do they do these things, and what on Earth do they have to do with each other?

The first thing to understand is that most central banks don’t actually print money. In the US, cash is actually printed by the Department of the Treasury. But cash is only a small part of the money in circulation. The monetary base consists of cash in vaults and in circulation; the US monetary base is about $3.6 trillion. The money supply can be measured a few different ways, but the standard way is to include checking accounts, traveler’s checks, savings accounts, money market accounts, short-term certified deposits, and basically anything that can be easily withdrawn and spent as money. This is called the M2 money supply, and in the US it is currently over $14.1 trillion. That means that only 25% of our money supply is in actual, physical cash—the rest is all digital. This is actually a relatively high proportion for actual cash, as the monetary base was greatly increased in response to the Great Recession. When we say that the Fed “prints money”, what we really mean is that they are increasing the money supply—but typically they do so in a way that involves little if any actual printing of cash.

The second thing to understand is that central banks don’t exactly set interest rates either. They target interest rates. What’s the difference, you ask?

Well, setting interest rates would mean that they made a law or something saying you have to charge exactly 2.7%, and you get fined or something if you don’t do that.

Targeting interest rates is a subtler art. The Federal Reserve decides what interest rates they want banks to charge, and then they engage in what are called open-market operations to try to make that happen. Banks hold reservesmoney that they are required to keep as collateral for their loans. Since we are in a fractional-reserve system, they are allowed to keep only a certain proportion (usually about 10%). In open-market operations, the Fed buys and sells assets (usually US Treasury bonds) in order to either increase or decrease the amount of reserves available to banks, to try to get them to lend to each other at the targeted interest rates.

Why not simply set the interest rate by law? Because then it wouldn’t be the market-clearing interest rate. There would be shortages or gluts of assets.

It might be easier to grasp this if we step away from money for a moment and just think about the market for some other good, like televisions.

Suppose that the government wants to set the price of a television in the market to a particular value, say $500. (Why? Who knows. Let’s just run with it for a minute.)

If they simply declared by law that the price of a television must be $500, here’s what would happen: Either that would be too low, in which case there would be a shortage of televisions as demand exceeded supply; or that would be too high, in which case there would be a glut of televisions as supply exceeded demand. Only if they got spectacularly lucky and the market price already was $500 per television would they not have to worry about such things (and then, why bother?).

But suppose the government had the power to create and destroy televisions virtually at will with minimal cost.
Now, they have a better way; they can target the price of a television, and buy and sell televisions as needed to bring the market price to that target. If the price is too low, the government can buy and destroy a lot of televisions, to bring the price up. If the price is too high, the government can make and sell a lot of televisions, to bring the price down.

Now, let’s go back to money. This power to create and destroy at will is hard to believe for televisions, but absolutely true for money. The government can create and destroy almost any amount of money at will—they are limited only by the very inflation and deflation the central bank is trying to affect.

This allows central banks to intervene in the market without creating shortages or gluts; even though they are effectively controlling the interest rate, they are doing so in a way that avoids having a lot of banks wanting to take loans they can’t get or wanting to give loans they can’t find anyone to take.

The goal of all this manipulation is ultimately to reduce inflation and unemployment. Unfortunately it’s basically impossible to eliminate both simultaneously; the Phillips curve describes the relationship generally found that decreased inflation usually comes with increased unemployment and vice-versa. But the basic idea is that we set reasonable targets for each (usually about 2% inflation and 5% unemployment; frankly I’d prefer we swap the two, which was more or less what we did in the 1950s), and then if inflation is too high we raise interest rate targets, while if unemployment is too high we lower interest rate targets.

What if they’re both too high? Then we’re in trouble. This has happened; it is called stagflation. The money supply isn’t the other thing affecting inflation and unemployment, and sometimes we get hit with a bad shock that makes both of them high at once. In that situation, there isn’t much that monetary policy can do; we need to find other solutions.

But how does targeting interest rates lead to inflation? To be quite honest, we don’t actually know.

The basic idea is that lower interest rates should lead to more borrowing, which leads to more spending, which leads to more inflation. But beyond that, we don’t actually understand how interest rates translate into prices—this is the so-called transmission mechanism, which remains an unsolved problem in macroeconomics. Based on the empirical data, I lean toward the view that the mechanism is primarily via housing prices; lower interest rates lead to more mortgages, which raises the price of real estate, which raises the price of everything else. This also makes sense theoretically, as real estate consists of large, illiquid assets for which the long-term interest rate is very important. Your decision to buy an apple or even a television is probably not greatly affected by interest rates—but your decision to buy a house surely is.

If that is indeed the case, it’s worth thinking about whether this is really the right way to intervene on inflation and unemployment. High housing prices are an international crisis; maybe we need to be looking at ways to decrease unemployment without affecting housing prices. But that is a tale for another time.