In the previous posts in this series, we’ve followed money from its origins as social ledger, through the plumbing of card payments, to the cat-and-mouse game of fraud detection. But all of that infrastructure operates within a framework set by institutions most people never think about: central banks. They decide how much money exists, how much it costs to borrow, and, in moments of crisis, whether the financial system survives. Here’s how they do it.
What a central bank actually does
A central bank is, at its core, the bank for banks. Commercial banks, the ones you and I have accounts with, maintain accounts at the central bank, just as we maintain accounts at our commercial bank. These accounts are called reserve accounts (or exchange settlement accounts, in the RBA’s terminology), and the money in them is the most “real” money in the system. When banks transfer money to each other (when they settle the payment obligations from all those card transactions and SWIFT messages) they settle through the central bank’s books.
Beyond being the banker’s bank, a central bank typically has three main jobs:
Monetary policy: managing the money supply and interest rates to pursue economic goals, usually price stability (keeping inflation low and stable) and, in some cases, full employment.
Financial stability: supervising banks, ensuring the payment system works, and acting as the lender of last resort when a bank runs out of cash.
Currency issuance: the central bank is the only institution authorised to print banknotes. (Coins are typically the government’s responsibility, not the central bank’s, a historical quirk.)
The relative emphasis varies. The US Federal Reserve has a dual mandate: maximum employment and stable prices. The European Central Bank has a single mandate: price stability (inflation close to but below 2%). The Reserve Bank of Australia has a mandate covering price stability, full employment, and “the economic prosperity and welfare of the people of Australia”, broadly similar to the Fed’s dual mandate. The Bank of Japan has struggled with the opposite problem from most central banks: not too much inflation, but too little, for decades.
Interest rates and the transmission mechanism
When the news says “the RBA raised interest rates by 25 basis points,” what actually happened?
The RBA sets a target for the cash rate: the interest rate on overnight loans between banks. Banks lend to each other overnight because at the end of each day, some banks have more reserves than they need (from receiving more payments than they sent) and some have fewer (from sending more than they received). These overnight loans smooth out the daily imbalances.
The RBA doesn’t directly command banks to charge a particular rate. Instead, it uses its control over the supply of reserves in the banking system to influence the rate. If the RBA wants the cash rate to go up, it drains reserves from the system (we’ll see how in a moment), making overnight reserves scarcer and therefore more expensive to borrow. If it wants the rate to go down, it adds reserves, making them abundant and cheap.
The cash rate is the anchor of the entire interest rate structure. When it moves, other rates follow: not instantly, and not one-for-one, but predictably. This is the transmission mechanism, the chain of cause and effect that connects the central bank’s decision to your mortgage payment.
Here’s how the chain works:
Cash rate moves: say the RBA raises it from 4.10% to 4.35%.
Wholesale funding costs rise. Banks fund themselves partly through the overnight market and partly through term deposits, bonds, and other instruments. Higher cash rates make all of these more expensive.
Banks raise lending rates. Variable-rate mortgages are typically priced as the cash rate (or bank bill swap rate) plus a margin. When the cash rate rises by 25 basis points, your variable mortgage rate usually rises by roughly 25 basis points too, although banks don’t always pass through the full amount immediately. CBA, Westpac, NAB, and ANZ all make their own decisions about pass-through, and the timing varies, usually within a few weeks.
Higher loan rates reduce borrowing. More expensive mortgages mean higher monthly payments, which means people have less money to spend on other things. Some people delay buying a home. Some businesses postpone investment. The economy cools.
Lower spending reduces inflation. With less demand for goods and services, businesses find it harder to raise prices. Inflation falls.
That’s the theory. The reality is messier. The transmission mechanism has long and variable lags, as Milton Friedman famously said. A rate change today might not fully affect inflation for 12 to 18 months. The central bank is driving by looking in the rear-view mirror, adjusting the steering wheel now for a curve it won’t reach for a year. This is why central banks sometimes overshoot: they raise rates too much and cause a recession, or too little and let inflation get entrenched.
Fixed-rate mortgages complicate things further. In Australia, about 60% of mortgages are variable-rate, so cash rate changes affect most borrowers fairly quickly. In the US, 30-year fixed-rate mortgages are the norm (thanks to the government-sponsored enterprises Fannie Mae and Freddie Mac, which created the market). An American who locked in a 3% mortgage in 2020 is barely affected by the Fed raising rates to 5.5% in 2023; their payments haven’t changed. This makes US monetary policy less immediately potent than Australian monetary policy, and it’s a significant structural difference.
Open market operations
So how does a central bank actually raise or lower the cash rate? Through open market operations: buying and selling government bonds in the open market.
When the central bank buys government bonds from a bank, it pays for them by crediting the bank’s reserve account. The bank now has more reserves and fewer bonds. More reserves in the system means more money available for overnight lending, which pushes the overnight rate down.
When the central bank sells government bonds to a bank, the bank pays by having its reserve account debited. The bank now has fewer reserves and more bonds. Fewer reserves in the system means less money available for overnight lending, which pushes the overnight rate up.
In practice, the RBA conducts open market operations most business days through repurchase agreements (repos). In a repo, the RBA buys bonds from a bank with an agreement to sell them back at a specified date and price. It’s a short-term collateralised loan. The RBA uses repos to fine-tune the supply of reserves to keep the cash rate close to the target.
The amounts are significant. The RBA’s daily open market operations typically involve billions of dollars. On any given day, the system might need an injection of $3-5 billion to maintain the target rate. The operations are routine and mechanical: the financial equivalent of adjusting a thermostat.
The Fed operates similarly but on a vastly larger scale. The Federal Reserve Bank of New York conducts open market operations through its Open Market Trading Desk (known as “the Desk”), buying and selling US Treasury securities and mortgage-backed securities. Before the 2008 crisis, the Fed’s balance sheet was about $900 billion. Today it’s around $7 trillion, a consequence of the massive bond-buying programs we’ll get to shortly.
Quantitative easing in plain English
In normal times, adjusting short-term interest rates is enough. The central bank moves the cash rate, other rates follow, and the economy responds. But in 2008, rates hit zero. The Fed had cut its target rate to 0-0.25% by December 2008 and couldn’t go lower. The economy was still in freefall. What do you do when your main tool stops working?
You invent a new one. Quantitative easing (QE) is what happens when a central bank buys enormous quantities of longer-term bonds, not to fine-tune overnight rates, but to push down interest rates across the entire yield curve and inject money directly into the financial system.
Here’s how it works. The Fed announces it will buy, say, $600 billion of US Treasury bonds over eight months (this was QE2, announced in November 2010). It buys these bonds from banks and other financial institutions, paying for them by creating reserves: literally adding numbers to the sellers’ accounts at the Fed. The money didn’t exist before the Fed created it.
The intended effects:
Lower long-term rates. By buying huge quantities of long-term bonds, the Fed pushes up bond prices. Bond prices and yields (interest rates) move inversely; when the price goes up, the yield goes down. Lower long-term rates make mortgages, corporate bonds, and other long-term borrowing cheaper.
Portfolio rebalancing. The institutions that sold bonds to the Fed now have cash instead of bonds. They don’t want to sit on cash earning nothing, so they invest in riskier assets: corporate bonds, stocks, real estate. This pushes up asset prices and lowers yields across the economy, making it cheaper for businesses to raise capital.
Signalling. QE tells the market that the central bank is serious about supporting the economy. Expectations matter enormously in economics. If businesses believe rates will stay low for a long time, they’re more likely to invest now.
Wealth effects. Rising asset prices make people who own assets feel wealthier, and wealthier people spend more. This is the most controversial channel, because it primarily benefits asset owners, disproportionately wealthier people. QE has been widely criticised for increasing wealth inequality, and the criticism has empirical support. A 2018 Bank of England working paper estimated that QE boosted UK household net worth by £600 billion in the first round alone, but the gains were concentrated among the wealthiest 5% of households.
The Fed conducted four rounds of QE between 2008 and 2014, buying over $3.5 trillion of bonds. The Bank of England bought £895 billion. The European Central Bank bought over €5 trillion. The Bank of Japan has been doing QE since 2001 and owns roughly half of all outstanding Japanese government bonds.
Did it work? The honest answer is: probably, partly. The counterfactual, what would have happened without QE, is impossible to observe. Most economists believe QE prevented a deeper recession and helped the recovery, but there’s genuine debate about how much of the economic improvement was due to QE versus fiscal policy (government spending) and natural recovery. The distributional effects, particularly wealth inequality, are harder to defend.
Quantitative tightening (QT) is the reverse. When the economy recovers and the central bank wants to normalise its balance sheet, it stops buying new bonds and lets existing ones mature without replacing them. Reserves drain from the system. Long-term rates rise. The process is slow and cautious because doing it too fast can destabilise financial markets, as the Fed discovered in 2019 when QT contributed to a sudden spike in overnight lending rates that forced an emergency intervention.
The Taylor Rule and how decisions get made
Central bank decisions aren’t made by gut feeling; they’re guided by frameworks, though the governors would insist they exercise “judgement” rather than follow rules mechanically.
The most famous framework is the Taylor Rule, proposed by Stanford economist John Taylor in 1993. It’s a simple formula:
Target rate = neutral rate + 0.5 x (inflation - target inflation) + 0.5 x (output gap)
The neutral rate is the interest rate that neither stimulates nor restrains the economy: the rate you’d set if everything were in balance. It’s not directly observable and has to be estimated, which is harder than it sounds. The RBA currently estimates Australia’s neutral rate at around 2.5-3.5%.
The output gap is the difference between actual GDP and potential GDP, how much slack there is in the economy. When the economy is running below capacity (high unemployment, idle factories), the gap is negative and the rule says to cut rates. When the economy is running hot (low unemployment, capacity constraints), the gap is positive and the rule says to raise rates.
No central bank follows the Taylor Rule mechanically. But research shows it explains actual rate decisions surprisingly well. When the Fed deviates significantly from what the Taylor Rule would prescribe, as it did in the early 2000s, keeping rates too low for too long by the rule’s standard, some economists blame the deviation for contributing to the housing bubble that led to the 2008 crisis. Taylor himself made this argument. Others disagree. The debate continues.
In practice, central bank boards (the RBA Board, the Fed’s Federal Open Market Committee, the ECB’s Governing Council) meet regularly (roughly every six weeks) and review a wide range of data: inflation, employment, wages growth, business confidence, housing prices, international developments, financial market conditions. The staff prepare detailed forecasts and briefings. Board members discuss and debate. Then they vote.
The minutes of these meetings are published (with a delay) and scrutinised intensely by financial markets. A single word change, “the Board will continue to consider” versus “the Board will continue to assess”, can move billions of dollars in bond markets. Central bank communication has become a policy tool in its own right. This is called forward guidance: telling the market what you plan to do in the future, so that market participants adjust their behaviour now, helping the policy work before you’ve even implemented it.
The RBA, the Fed, the ECB: same job, different styles
All major central banks do roughly the same thing, but their institutional structures and cultures vary significantly.
The Reserve Bank of Australia is relatively small and relatively transparent by international standards. The Governor (currently Michele Bullock, the first woman to hold the role, appointed in 2023) chairs a nine-member Board that includes the Treasury Secretary and seven external members. The RBA publishes a monetary policy statement after each meeting and holds a press conference. An independent review in 2023 (the Hayne-Debelle review) recommended significant governance reforms, including restructuring the Board to include more economic expertise and creating a separate Monetary Policy Board. Reforms based on the review began in 2024.
The US Federal Reserve is Byzantine in its complexity. It’s not one institution but a system: a Board of Governors in Washington (seven members, appointed by the President and confirmed by the Senate), twelve regional Federal Reserve Banks (each with its own president, board, and research staff), and the Federal Open Market Committee (FOMC), which makes monetary policy decisions. The FOMC comprises the seven Governors plus five of the twelve regional bank presidents on a rotating basis (the New York Fed president always has a vote; the others rotate).
The Fed’s independence is fiercely defended. The Chair (currently Jerome Powell, first appointed by Trump in 2018, reappointed by Biden in 2022) serves a four-year term but can only be removed “for cause,” not for policy disagreements. Presidents have tried to pressure Fed Chairs (Nixon leaned heavily on Arthur Burns before the 1972 election, and Trump publicly attacked Powell for not cutting rates fast enough) but the institutional norms have generally held.
The European Central Bank has the hardest job. It sets a single monetary policy for twenty countries with very different economies. A rate that’s appropriate for Germany might be too high for Greece and too low for Ireland. The ECB’s Governing Council has 26 members (six Executive Board members plus the central bank governors of all eurozone countries), making it one of the largest monetary policy committees in the world. Decisions are made by simple majority, but in practice the ECB seeks consensus.
The ECB has a reputation for hawkishness: an institutional aversion to inflation that reflects Germany’s historical trauma with hyperinflation in the Weimar Republic (1921-1923, when prices doubled every few days). This hawkishness was visible in 2011, when the ECB raised rates during the European sovereign debt crisis, a decision many economists consider a significant policy error that deepened the eurozone recession.
The Bank of Japan is the outlier. Japan has been fighting deflation, falling prices, since the early 1990s, when a massive asset bubble burst. The BOJ was the first major central bank to adopt zero interest rates (1999), the first to adopt QE (2001), and the first to adopt yield curve control (2016): a policy where the central bank targets not just the short-term rate but the entire yield curve, buying whatever quantity of bonds is necessary to keep 10-year government bond yields near zero.
Under Governor Haruhiko Kuroda (2013-2023), the BOJ pursued the most aggressive monetary easing in history, buying bonds, stocks (through ETFs), and real estate investment trusts. The BOJ now owns roughly half of the Japanese government bond market and is one of the largest holders of Japanese equities. When economists talk about the limits of monetary policy, Japan is exhibit A.
Central bank independence and why it matters
Why can’t the government just tell the central bank what to do? Many governments have tried. The results are instructive.
The argument for independence is straightforward: politicians face elections and have short time horizons. The temptation to cut rates before an election (boosting the economy in the short run) or to print money to fund spending (avoiding unpopular taxes) is powerful. If the government controls monetary policy, the result, historically, is inflation.
The textbook example is the Nixon-Burns era. Arthur Burns, Fed Chair from 1970 to 1978, came under intense pressure from President Nixon to keep rates low before the 1972 election. Secretly recorded White House tapes reveal Nixon telling Burns, “We’ll take inflation if necessary, but we can’t take unemployment.” Burns accommodated. Inflation rose from 5.5% in 1970 to 11% by 1974, and the US entered a decade of stagflation (simultaneously high inflation and high unemployment) that wasn’t tamed until Paul Volcker raised rates to 20% in 1981, triggering a severe recession but breaking inflation’s back.
Volcker’s intervention is the canonical example of why central bank independence matters. His rate hikes were extraordinarily unpopular. Farmers blockaded the Fed building with tractors. Car dealers mailed coffins containing the keys to unsold vehicles. Members of Congress called for his resignation. But he persisted, and inflation fell from 13% to 3% over three years. A politician facing re-election could not have done what Volcker did.
Turkey provides a contemporary case study. President Erdogan has repeatedly fired or forced out central bank governors who raised rates. Between 2019 and 2023, Turkey had four different central bank governors. Erdogan believes, contrary to mainstream economics, that high interest rates cause inflation rather than curbing it. The Turkish lira lost roughly 80% of its value against the US dollar between 2018 and 2023, and inflation hit 85% in October 2022. After the June 2023 elections, Erdogan appointed a new economic team that returned to orthodox policy and raised rates sharply. The episode is a real-time experiment in what happens when central bank independence is overridden.
The evidence broadly supports independence. A classic 1993 paper by Alberto Alesina and Lawrence Summers found a strong negative correlation between central bank independence (measured by various institutional indices) and inflation: countries with more independent central banks had lower and more stable inflation, with no apparent cost in terms of output or employment. The finding has been replicated and refined many times since.
But independence isn’t absolute, and it shouldn’t be. Central banks derive their authority from legislation, and legislatures can change the law. The democratic accountability comes through the mandate. Parliament tells the RBA what to achieve (price stability, full employment) but not how to achieve it. The central bank has instrument independence (it chooses the tools) but not goal independence (it doesn’t choose the objectives). If a central bank consistently fails to achieve its mandate, the government can and should reform the institution, as the 2023 RBA review recommended.
Lender of last resort
The final critical function is the one you hope never activates: the central bank as lender of last resort.
When a bank runs out of cash (not because it’s insolvent, with liabilities exceeding assets, but because it’s temporarily illiquid, holding assets it can’t sell fast enough to meet withdrawals) the central bank can lend to it against collateral. This prevents bank runs from becoming self-fulfilling prophecies. If depositors know the central bank will backstop their bank, they’re less likely to panic and withdraw, which means the backstop is less likely to be needed. It’s a confidence mechanism.
Walter Bagehot, editor of The Economist in the 19th century, codified the doctrine in Lombard Street (1873): in a crisis, the central bank should lend freely, at a high rate, against good collateral. Freely, to stop the panic. At a high rate, to discourage banks from relying on the facility in normal times. Against good collateral, to protect the central bank from losses.
The 2008 financial crisis tested this doctrine to its limits. The Fed lent over $1.2 trillion through emergency facilities to banks, investment banks, insurers (AIG), money market funds, and even foreign central banks. It extended facilities that Bagehot never imagined: lending against collateral that wasn’t obviously “good” and at rates that weren’t obviously “high.” The argument was that the alternative, letting the financial system collapse, was worse.
The RBA was less dramatically tested in 2008 (Australia didn’t have a banking crisis, thanks partly to stricter regulation and partly to the mining boom) but activated its own emergency facilities during the COVID-19 pandemic in March 2020. The Term Funding Facility lent $188 billion to Australian banks at a fixed rate of 0.10%, ensuring they could continue lending to businesses and households. The facility closed to new drawdowns in June 2021, and the loans are being repaid.
Why your mortgage rate changed
Pull all of this together and you can trace the chain from a committee meeting in Martin Place, Sydney, to your monthly payment.
In May 2022, the RBA raised the cash rate for the first time in eleven years, from 0.10% to 0.35%. Over the following eighteen months, it raised rates twelve more times, to 4.35% by November 2023. Each increase was a decision by nine people around a table, informed by data, forecasts, and judgement.
Each increase rippled through the transmission mechanism. Wholesale funding costs rose. Banks repriced their variable-rate mortgages. A borrower with a $500,000 variable-rate mortgage at 2.5% in April 2022 was paying about $2,240 per month in principal and interest. By November 2023, with the rate at around 6.5%, the same borrower was paying about $3,160 per month: an increase of $920 per month, or roughly $11,000 per year.
That increase was the RBA’s monetary policy working exactly as intended. Higher mortgage payments meant less discretionary spending. Less spending meant less demand. Less demand, eventually, slowly, with those long and variable lags, meant lower inflation.
The human cost was real. The RBA’s own research showed that about 5% of variable-rate mortgage holders were in severe financial stress by late 2023, spending more than 30% of their income on mortgage payments. This is the trade-off that central bankers face: short-term pain for long-term price stability. It’s the least bad option, but it’s not a painless one, and the people who bear the cost are not the same people who sit around the table making the decision.
The quiet machine
Central banks are, by design, boring. They employ thousands of economists, publish hundreds of research papers, and hold press conferences where every word is weighed for market impact. They’re the infrastructure of monetary economies: essential, largely invisible, and only noticed when something goes wrong.
But they operate within a system that’s changing fast. Cryptocurrencies promise to bypass central banks entirely. Central Bank Digital Currencies (CBDCs) promise to modernise them. The technology of money is shifting, and the institutions that manage it are having to decide how to respond.
That’s where we’re headed next. How Crypto Actually Works strips back the hype and the scepticism to explain what blockchain technology genuinely does, what problem Bitcoin actually solved, and whether any of it matters.