Skip to content

Financial Management · The nature and role of money markets

Interest Rates and Yield Determination for ACCA FM

Updated 11 October 2026 · Fact-checked

Interest rates are the price of borrowing money. Money market rates are set by supply and demand for funds, guided by the central bank's policy rate. A lender's yield reflects the real rate, expected inflation, and premiums for risk, term and illiquidity. The yield curve plots yield against maturity.

Understand Interest Rates and Yield Determination

An interest rate is the price of using someone else's money for a period. Like any price, it comes from supply and demand. Savers and lenders supply funds. Borrowers demand them. When demand for funds rises or supply falls, rates rise.

The central bank sits at the centre of the money market. It sets a policy rate and lends to banks at or near that rate. Banks then price their own lending and borrowing off it. The rate at which banks lend to each other for short periods is the interbank rate. It moves closely with the policy rate. If the central bank raises its rate, interbank rates, deposit rates and loan rates usually follow. The central bank can also change the supply of money, for example by buying or selling securities.

The yield a lender demands is built up in layers. Start with a real rate for giving up spending today. Add expected inflation to protect purchasing power. Then add premiums for default risk (the borrower may not pay), for term (money tied up longer is riskier) and for illiquidity (the asset is hard to sell quickly). Government securities carry little default risk, so corporate borrowers pay a credit spread above them.

The yield curve plots yield against time to maturity for similar securities. It can be upward sloping (normal), flat, or downward sloping (inverted). Three theories explain its shape. Expectations theory: long rates are an average of expected future short rates, so a rising curve means the market expects rates to rise. Liquidity preference theory: investors prefer short-term lending, so they demand a premium for longer terms. This makes the curve slope up even if rates are expected to stay flat. Market segmentation theory: separate groups of lenders and borrowers operate at different maturities, and each segment sets its own rate by its own supply and demand.

Key rules to remember

Fisher equation (exact)
(1 + money rate) = (1 + real rate) × (1 + inflation rate)
Money (nominal) rate includes inflation. Real rate removes it. Rearrange to find the real rate.
Real rate
Real rate = (1 + money rate) ÷ (1 + inflation) − 1
Use this when asked for the exact real rate. The approximation money rate − inflation is only rough.
Build-up of a required yield
Required yield = real rate + expected inflation + default risk premium + liquidity premium + maturity premium
A conceptual build-up, not a precise calculation. Use it to explain why two securities have different yields.
Credit spread
Credit spread = corporate yield − risk-free yield (same maturity)
Wider spread means the market sees more default risk.
Implied forward rate (expectations theory)
(1 + r2)² = (1 + r1) × (1 + f)
r1 and r2 are one-year and two-year spot yields. f is the implied one-year rate starting in a year.

How to solve Interest Rates and Yield Determination questions

Use this approach for any question on rate determination, yield curves or real versus nominal rates.

  1. 1Read the question and decide what is asked: a calculation (real rate, forward rate) or an explanation (why rates differ or the curve slopes).
  2. 2Identify the security: government or corporate, short or long term, easily traded or not.
  3. 3For a calculation, write the formula first and put the rates in as decimals.
  4. 4For a nominal and real rate question, use the exact Fisher equation unless told to approximate.
  5. 5For a curve question, name the theory that fits the clue: expected future rates (expectations), premium for tying up money (liquidity preference), separate markets (segmentation).
  6. 6For central bank questions, trace the chain: policy rate changes, interbank rates move, then bank deposit and loan rates follow.
  7. 7Check your answer is sensible: real rate below nominal when inflation is positive, long yield above short on an upward curve.
  8. 8In written parts, link each point to the scenario and state the effect on the company's borrowing or investing.

Quickest way: Clue-matching for objective questions

When to use it: Section A and OT case questions where you pick one option in under two minutes.

  1. Spot the key phrase. 'Expected future short rates' points to expectations theory.
  2. 'Premium for lending longer' or 'prefer liquidity' points to liquidity preference.
  3. 'Different groups of investors at different maturities' points to market segmentation.
  4. For real rates, divide: (1 + nominal) ÷ (1 + inflation) − 1. Do it on the calculator once and check the sign.
  5. For forward rates, compare (1 + r2)² with (1 + r1) and divide.
  6. Eliminate options that confuse the central bank's policy rate with a market yield.

Common mistakes in Interest Rates and Yield Determination

  • Using nominal minus inflation when the question asks for the exact real rate.

    The subtraction is a quick approximation students remember.

    Fix: Use (1 + nominal) ÷ (1 + inflation) − 1 unless the question says to approximate.

  • Saying liquidity preference theory explains an upward curve only because rates are expected to rise.

    Students mix it up with expectations theory.

    Fix: Liquidity preference adds a premium for longer terms. The curve slopes up even with flat expected rates.

  • Saying an inverted yield curve is impossible under liquidity preference.

    Students think the premium always forces an upward slope.

    Fix: An inverted curve can occur if expected falls in future short rates outweigh the premium.

  • Treating the central bank as setting every interest rate directly.

    Students overstate the central bank's control.

    Fix: It sets the policy rate and influences market rates. Credit risk, term and demand still determine the rates on individual loans and securities.

  • Forgetting the square in the forward rate calculation.

    Students divide yields instead of compounding them.

    Fix: Write (1 + r2)² first. Then divide by (1 + r1) and subtract 1.

  • Listing risk, term and liquidity without applying them to the scenario.

    Students memorise lists in written answers.

    Fix: State which factor applies to the named borrower and whether it raises or lowers the yield.

Worked examples

Example 1

A bank deposit pays a money (nominal) rate of 8% a year. Expected inflation is 5%. Calculate the real rate of interest, to two decimal places, and compare it with the approximation.

Show the solution
  1. Write the exact formula: real rate = (1 + money rate) ÷ (1 + inflation) − 1.
  2. Substitute: 1.08 ÷ 1.05 − 1.
  3. 1.08 ÷ 1.05 = 1.028571.
  4. Subtract 1: 0.028571, which is 2.86%.
  5. The approximation 8% − 5% gives 3%, which is slightly higher.

Answer: The exact real rate is 2.86% a year. The approximation of 3% overstates it slightly.

Example 2

One-year spot yield is 4% and two-year spot yield is 5%. Using expectations theory, calculate the implied one-year rate starting in one year's time. Explain what the result suggests about the yield curve.

Show the solution
  1. Use (1 + r2)² = (1 + r1) × (1 + f).
  2. (1.05)² = 1.1025.
  3. Divide by (1 + r1): 1.1025 ÷ 1.04 = 1.060096.
  4. Subtract 1: f = 6.01% (to two decimal places).
  5. The implied future one-year rate (6.01%) is above both spot rates, so the market expects short rates to rise.

Answer: The implied forward rate is about 6.01%. Under expectations theory, the upward-sloping curve reflects expected rises in short-term rates.

Exam tips

  • Know the three theories by their key idea. Objective questions usually give a one-line clue and ask you to match it.
  • For real and nominal rates, use the exact Fisher formula unless the question tells you otherwise.
  • In written answers, apply each factor (risk, term, liquidity) to the company in the scenario. Do not just list them.
  • Explain central bank effects as a chain from policy rate to interbank rate to loan and deposit rates, then to the company's cost of borrowing.
  • Section A answers are all or nothing. Check the sign and the size of your answer before you select.

Practice questions from The nature and role of money markets

Interest Rates and Yield Determination in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Interest Rates and Yield Determination: frequently asked questions

What factors affect interest rates in ACCA FM?

Supply and demand for funds, central bank policy, expected inflation, default risk, the length of the loan and how easily the asset can be sold. Higher risk, longer term or lower liquidity each push the required yield up.

What are the yield curve theories in ACCA Applied Skills?

Expectations theory says the curve reflects expected future short rates. Liquidity preference theory adds a premium for longer maturities. Market segmentation theory says each maturity has its own supply and demand.

How does a central bank affect money market rates?

It sets a policy rate at which it lends to banks and may buy or sell securities to change the supply of money. Banks price interbank lending, deposits and loans off that rate, so market rates generally move with it.

What is the difference between nominal and real interest rates?

The nominal (money) rate is the quoted rate and includes compensation for inflation. The real rate removes inflation and shows the gain in purchasing power. They are linked by (1 + nominal) = (1 + real) × (1 + inflation).