IB Economics Monetary Policy (HL)

What Happens When There's Too Much Or Not Enough Money? The Market for Money Explained

Target Question

What is the demand and supply of money and how is the interest rate determined?

Let's go back to the year 2009 for a second as this is the perfect introduction to today's topic. So, let's imagine it's 2009. The global financial system has just collapsed. Banks are refusing to lend to each other. Businesses can't get credit. Unemployment is causing chaos in most economies. Central banks around the world are panicking - and their go-to instrument, cutting interest rates, is already reaching a point where no more progress can be made. The US Federal Reserve has slashed rates to basically zero. The Bank of England isn't far behind.

At this stage my students usually ask me the following question, if money is cheap to borrow, why isn't anyone borrowing? Why isn't anyone spending?

To answer this question and explain today's entry we need to understand something most people never think about: money itself has a market. Just like apples, concert tickets, or a pair of Nike Air Jordan's money has supply, demand, and a price. Where does the price of money come from? You already know it. It's called the interest rate.

The Market for Money: Supply and Demand

The Demand for Money (DM)

The demand for money specifically refers to the desire to hold money in liquid form - cash in your pocket or in your current account - rather than saving or investing it.

So, the demand for money: is the desire to hold money in liquid form rather than saving or investing it, driven by transaction, precautionary, and speculative motives. The demand for money has an inverse relationship with interest rates.

Why would anyone want to hold cash rather than saving it and earning interest? A few reasons:

• Transactions: You need cash to buy stuff. Your daily coffee, train ticket, Netflix subscription - all require liquid money.

• Precaution: People like a financial cushion for unexpected expenses. Your car breaks down, your phone screen cracks, you have to pay an surprise visit to the dentist - that rainy-day fund is liquid money being held, not saved.

• Speculation: Sometimes people hold cash while waiting for a better investment opportunity.

However, there is a key relationship you need to learn: the demand for money and the interest rate move in opposite directions. When interest rates are high, holding cash is expensive - you're giving up the return you could earn on savings. That's the opportunity cost of holding money. So people hold less cash and save more. When rates fall, the opportunity cost drops and people are more willing to sit on liquid cash. The DM curve slopes downward.

The Supply of Money (SM)

The supply of money is the total amount circulating in the economy - notes, coins, bank deposits, loans, credit. All of it.

So, the supply of money: is the total quantity of money circulating in an economy - including notes, coins, bank deposits, loans, and credit - controlled by the central bank and represented as a vertical curve on the money market diagram.

The SM curve is vertical. Not downward sloping. Not upward sloping. A straight vertical line. Why?

Because the money supply is controlled by the central bank, not by market forces. The central bank decides how much money exists in the economy through its policy tools - and it doesn't change that amount based on interest rates. It's a policy decision, full stop. So the supply is fixed at any given point, and that is why we have a vertical curve.

The Equilibrium Interest Rate

Where DM and SM intersect, you get the equilibrium interest rate - the price of money that clears the market.

So, the equilibrium interest rate is determined by the intersection of the demand for money and supply of money curves. When money demand exceeds supply, interest rates rise; when supply exceeds demand, rates fall.

• If the interest rate is below equilibrium: demand for money exceeds supply (DM > SM). People want more money than is available → competition for funds → interest rates rise back toward equilibrium.

• If the interest rate is above equilibrium: supply exceeds demand (SM > DM). More money is floating around than people want to hold → rates fall back toward equilibrium.

The central bank can shift the SM curve - move it left (reduce money supply, raise rates) or right (increase money supply, lower rates) - to achieve its policy targets. That's monetary policy live, right there on the diagram.

• Internal Assessment (IA) Guide – Free Download
  Step-by-step support on topic selection, structure, evaluation, and most common IB Economics IA mistakes.

• Understanding key IB Economics Internal Assessment concepts

• Applying and explaining them in real-world IB Economics contexts

• Building IB Economics IA confidence without drowning in dry theory and explanations.

Download the IA guide now for free and boost your IB Economics grades and confidence

Not One Interest Rate, But Many

There is no single interest rate in an economy. There's actually a whole structure of different rates, each attached to a different type of loan or market:

• Short-term overdrafts → typically higher rates

• Credit card debt → often the highest rates of all (ever checked the APR on a credit card? It'll make your eyes water)

• Long-term mortgages → lower, but over a much longer period

• Government borrowing → the lowest rates, because lending to a government is considered very safe

And that last point brings us to credit risk. The riskier a borrower, the higher the interest rate a lender will charge to compensate for the chance of not being paid back. A multinational company with a sterling credit rating? Cheap loan. An individual with a patchy credit history? Much more expensive. It is all about the perceived amount of risk involved in the transaction.

This is why your credit score is an important tool - it directly affects the interest rate you'll pay when you need to borrow. In the near future you will remember your Economics teachers, trust me.

M1, M2 and M3: The Money Supply Isn't One Thing

My HL students need to know that economists don't measure the money supply as one big lump. They break it down into levels, from most liquid to least:

M1 - The Narrow Money Supply The most liquid measure. Includes physical currency (notes and coins in circulation) plus demand deposits - like your current account that you can access instantly. If you can spend it right now, it's in M1.

So, M1 is the narrowest measure of money supply, comprising physical currency and instantly accessible demand deposits.

M2 - Broader Money Everything in M1, plus near-money - savings accounts, money market securities, and short-term time deposits like certificates of deposit (CDs). These can't be accessed instantly, but they can be converted to cash fairly quickly.

So, M2 is a broader measure including M1 plus near-money such as savings deposits and short-term time deposits.

M3 - Broad Money The largest measure. Everything in M1 and M2, plus larger time deposits, institutional money market funds, and other bigger liquid assets. This is the one used to evaluate the entire money circulation in an economy.

So, M3 is the broadest measure, including M1, M2, and larger institutional deposits and liquid assets.

Putting it all together it becomes something like this, M1 is the cash in your pocket, M2 includes your savings account, and M3 adds in the sophisticated financial instruments that big institutions and pension funds are working with.

So is this relevant? Yes. When central banks talk about "the money supply," they need to specify which measure they mean. The BoE monitors M4 (a UK-specific version of M3). The ECB watches M3 closely as part of its two-pillar strategy for choosing policy.

Real vs Nominal Interest Rates

Right, this one always causes a lot of trouble in class.

The nominal interest rate is the rate you actually agree with your bank. It's the headline number often shown in the news. Your savings account offers 4%? That's nominal.

So, the nominal interest rate is the stated rate of interest agreed between a lender and borrower, unadjusted for inflation.

The real interest rate is what you actually earn or pay, once you adjust for inflation.

So, the real interest rate is the nominal interest rate minus the rate of inflation. A real interest rate can be negative if inflation exceeds the nominal rate.

The formula is simple:

Real Interest Rate = Nominal Interest Rate − Inflation Rate

IB Economics Example time:

Your savings account pays 1% nominal interest. Inflation is running at 2.5%. Your real interest rate is:

1% − 2.5% = −1.5%

That's a negative real return. Your savings are growing in nominal terms, but they're actually losing purchasing power in real terms. The money in your account buys less after a year than it did before, even though the actual number in your account went up slightly. Inflation ate your return at breakfast time.

IB Economics Real-life Example: Between 2021 and 2023, millions of UK savers experienced this. While the BoE base rate sat at rock-bottom levels and savings accounts offered near-zero returns, inflation spiked above 10%. Real interest rates were deeply negative - meaning savers were, in effect, paying for the privilege of keeping money in the bank. Not a great situation to be in.

This distinction is crucial for evaluating how effective monetary policy really is. Cutting the nominal rate is the tool - but it's the real rate that actually influences decisions and behaviour. If inflation is high, even a nominally low rate might not feel cheap to borrowers in real terms.

For access to all IB Economics exam practice questions, model answers, IB Economics complete diagrams together with full explanations, and detailed assessment criteria, explore the Complete IB Economics Course

Closing the Gaps: Expansionary vs Contractionary Monetary Policy

This is where everything makes sense with the AD/AS diagrams.

Scenario 1: The Deflationary Gap (Recessionary Gap)

The economy is operating below full employment (Y1 < YF). Real GDP is underperforming. Unemployment is rising. The government needs to stimulate demand.

Response → Expansionary monetary policy: cut interest rates

Here's what happens across the AD components:

• Consumption (C) ↑ - cheaper mortgages and loans → households spend more

• Investment (I) ↑ - cheaper business credit → firms expand and hire

• Net Exports (X−M) ↑ - lower interest rates → currency depreciates → exports cheaper → foreign demand rises

All of this shifts AD to the right (AD1 → AD2), increasing real GDP from Y1 toward YF and closing the deflationary gap. The average price level also rises slightly (PL1 → PL2) - but this time is a controlled, acceptable side effect.

Scenario 2: The Inflationary Gap

The economy is overheating - operating above full employment. Inflation is rising. The central bank needs to cool things down.

Response → Contractionary monetary policy: raise interest rates

• Consumption ↓ - mortgages and loans get pricier → households pull back

• Investment ↓ - businesses face higher borrowing costs → expansion slows

• Net Exports ↓ - higher rates attract foreign capital → currency appreciates → exports more expensive

AD shifts left (AD1 → AD2), bringing real GDP back from above YF toward the full employment level, and reducing the price level from PL1 toward PL2. Inflationary gap: closed.

IB Economics Real-life Example: This is exactly what the BoE and ECB were doing between 2022 and 2024. A typical contractionary response to a regular inflationary gap - driven initially by post-COVID demand surges and supply-side energy shocks. Interest Rates went up. Mortgages got nasty. The economy cooled.

Does Monetary Policy Actually Work? An Honest Assessment

Examiners want you to think critically - not just mention the theory time and time again.

Strengths of Monetary Policy

1. Flexible, incremental, and reversible Interest rate changes can be made in small steps (the BoE typically moves in 0.25% increments), monitored for effect, and reversed if needed. No need to pass legislation. No committee votes in Parliament. The Monetary Policy Committee meets, decides, announces - and it is done. Compare that to fiscal policy, where a change to income tax requires a Budget, legislation, and months of lead time.

2. Politically independent Because the central bank is independent from the elected government, monetary policy decisions are (in theory) made on economic merit rather than on vote calculations. No cutting interest rates before an election to make everyone feel good.

3. Faster implementation than fiscal policy A rate decision can be announced and implemented almost immediately. Fiscal policy changes - new tax bands, infrastructure spending - take months or years to flow through the economy.

Every episode of Pint-Sized links back to what matters most for your IB Economics course:

• Understanding key IB Economics concepts

• Applying them in real-world IB Economics contexts

• Building IB Economics course confidence without drowning in dry theory.

Subscribe for free to exclusive episodes designed to boost your IB Economics grades and confidence

Weaknesses and Constraints of Monetary Policy

1. The zero lower bound problem Interest rates can't realistically go much below zero - there's a floor. When rates are already near-zero, there's almost no room left to stimulate further through conventional monetary policy. The 2008 financial crisis and the COVID-19 pandemic both exposed this in an obvious way.

IB Economics Real-life Example: Japan has battled with near-zero or negative rates since the 1990s - a phenomenon economists call the liquidity trap - with limited success. More on that below.

2. The confidence problem - as we mentioned before, you can lead a horse to water but... Even with rates at rock bottom and borrowing at an extremely cheap level, if consumers are terrified about losing their jobs and businesses are scared about demand collapsing, the reality is that nobody borrows and nobody spends. The transmission mechanism - the chain from rate cut to increased spending - breaks down when confidence evaporates. This is exactly what happened in 2009. Rates were at historic lows. The economy stopped for years.

3. Time lags Even when monetary policy does work, its effects take time. The BoE estimates that interest rate changes take up to 18 months to fully work through the economy. By then, the economic conditions may have changed completely. The central bank could be fighting yesterday's problem.

4. Global interdependence In an open, globalised economy, domestic monetary policy never functions in isolation. Capital flows in and out based on international rate differentials. If the Fed raises rates while the BoE holds, capital flows to the US, affecting the pound. This applies particularly to small open economies as they can find their monetary policy effectiveness undermined by external forces.

The Liquidity Trap

A liquidity trap occurs when interest rates are already so low that cutting them further has no effect on spending or borrowing. People and businesses would rather sit on cash than invest or spend, regardless of how cheap borrowing gets. Conventional monetary policy becomes essentially useless.

So, a Liquidity trap is a situation in which interest rates are already near zero and further cuts fail to stimulate borrowing or spending, rendering conventional monetary policy ineffective.

Keynes first identified this idea in the 1930s during the Great Depression. Japan survived it for three decades starting in the 1990s. And after 2008, much of the Western world went through the experience - this is why central banks turned to the unconventional tool of quantitative easing (QE) to basically inject money directly into the economy when interest rate cuts stopped working.

IB Economics Diagrams Programme, What's included:

• 200+ exam-ready diagrams covering the entire IB Economics syllabus

• Video for every diagram showing you exactly how each model looks

• Image version perfect for modelling diagrams in you essays, presentations, and your IA

• Detailed written explanations of the IB Economics theory behind each diagram

• Both SL and HL IB Economics diagrams clearly labelled and organised by topic

• Real IB Economics exam application showing how to use diagrams effectively in Paper 1 and Paper 2

Frequently Asked Questions

Q1: How is the interest rate determined in economics? The interest rate is determined by the interaction of the demand for money and the supply of money. When money demand exceeds supply, rates rise. When supply exceeds demand, rates fall. The central bank can shift the money supply curve to target a specific interest rate.

Q2: What is the difference between nominal and real interest rates? The nominal interest rate is the headline rate that appears on the news agreed between lender and borrower. The real interest rate adjusts for inflation: Real Rate = Nominal Rate − Inflation Rate. If inflation is higher than the nominal rate, the real interest rate is negative - meaning savings are losing purchasing power.

Q3: What is the difference between M1, M2, and M3? M1 is the narrowest measure - cash and instantly accessible deposits. M2 adds near-money like savings accounts and short-term deposits. M3 is the broadest, adding large institutional deposits and money market funds. Categories go from most liquid (M1) to the least liquid (M3).

Q4: What is a liquidity trap and why is it relevant? A liquidity trap occurs when interest rates are already near zero and further cuts fail to stimulate spending - because households and businesses prefer to hold cash rather than borrow and invest. It's a key limitation of monetary policy, seen in Japan since the 1990s and in Western economies after the 2008 financial crisis.

Q5: What are the strengths and weaknesses of monetary policy? Strengths: flexible, reversible, fast to implement, and politically independent. Weaknesses: limited effectiveness at the zero lower bound, reliant on consumer and business confidence, subject to time lags of up to 18 months, and vulnerable to global capital flows in open economies.

Stay well

Explore Topics:

IB Economics Hub Page your IB Economics daily guide

IB Economics Macroeconomics Hub Page access Monetary Policy here as well as the rest of the module

IB Economics The Business Cycle Hub Page - useful information when discussing deflationary and inflationary gaps

IB Economics Diagrams Page Check Unit 22 for All Monetary Policy diagrams with explanations

IB Economics Activity book Page Module 3 Macroeconomics Unit 3.15 for Monetary Policy exam practice, activities, model answers and IB Economics Marking schemes

IB Economics Monetary Policy Page (Tools and Overview) - essential reading

IB Economics Inflation Hub Page - essential learning when discussing real vs nominal rates and inflationary gaps

IB Economics Fiscal Policy Hub Page for exploring in depth the contrast between Monetary Policy and Fiscal Policy strengths and limitations of both.

IB economics Calculations Book make sure you check unit 21 for Monetary Policy calculations exercises, IB model answers, and IB marking schemes

Read Next: IB Economics Fiscal Policy Government Intervention