Welcome to Risk Management: Why Do Rates Move?

Hello there! Welcome to one of the most practical parts of your FM studies. Have you ever wondered why a holiday to the USA costs more this year than last, or why your bank suddenly changes the interest rate on your savings? In this chapter, we explore the "why" behind these changes. Understanding these movements is the first step toward managing financial risk.

Don't worry if these concepts seem a bit abstract at first. We are going to break them down into simple "real-world" ideas. By the end of these notes, you’ll see that currency and interest rates follow a logic that actually makes a lot of sense!

1. Causes of Exchange Rate Fluctuations

An exchange rate is simply the "price" of one currency expressed in terms of another. Just like the price of coffee or smartphones, the price of a currency is driven by supply and demand. If everyone wants to buy US Dollars, the price of the Dollar goes up (it appreciates).

But what makes people want to buy or sell a currency? There are four main theories you need to know for your exam:

A. Purchasing Power Parity Theory (PPPT)

This theory focuses on inflation. In simple terms: if inflation is high in the UK, the Pound (\(£\)) will lose its "purchasing power." As a result, the value of the Pound should fall compared to currencies with lower inflation.

The Logic: If a loaf of bread costs \(£1\) in London and \(\$1.30\) in New York today, the exchange rate should be \(1:1.30\). If UK prices double but US prices stay the same, the exchange rate must adjust so that the bread still "costs the same" effectively in both places.

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The Formula:
\n\( S_1 = S_0 \times \frac{1 + i_c}{1 + i_b} \)
\nWhere:
\n\( S_1 \) = Expected future spot rate
\n\( S_0 \) = Current spot rate
\n\( i_c \) = Inflation rate in country C (the "counter" currency)
\n\( i_b \) = Inflation rate in country B (the "base" currency)

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Quick Tip: In the exam, PPPT is used to predict future spot rates. If the question gives you two inflation rates and asks what the exchange rate will be in one year, use this formula!

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B. Interest Rate Parity Theory (IRPT)

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This theory focuses on interest rates. It suggests that the difference between the spot exchange rate and the forward exchange rate is caused by the difference in interest rates between two countries.

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The Logic: If you could get a 10% interest rate in the UK and only 2% in the USA, everyone would move their money to the UK. To prevent everyone from doing this and "printing free money," the exchange rate adjusts. The currency with the higher interest rate will trade at a forward discount (it will be cheaper in the future) to offset the gain from the high interest.

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The Formula:
\n\( F_0 = S_0 \times \frac{1 + i_c}{1 + i_b} \)
\n(Note: This looks almost identical to the PPPT formula, but uses interest rates instead of inflation!)

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C. The Balance of Payments

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This is like a country’s bank statement. If a country exports more than it imports (a surplus), foreigners need to buy that country’s currency to pay for the goods. This high demand makes the currency stronger.

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D. Speculation and Sentiment

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Sometimes, rates move just because people think they will. If currency traders believe the Euro will get stronger, they buy it now. This massive buying actually causes the Euro to get stronger! It’s a self-fulfilling prophecy.

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Key Takeaway: Inflation (PPPT) predicts future spot rates, while Interest Rates (IRPT) explain the forward rate. If inflation goes up, the currency value usually goes down!

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2. Causes of Interest Rate Fluctuations

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Interest rates are the "cost of borrowing" or the "reward for saving." They don't stay still because several forces are constantly pushing them up or down.

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A. The Fisher Effect

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This is a crucial concept for FM students. It explains the relationship between inflation and interest rates. Investors want a "real" return. If inflation is 5%, and a bank only pays 5% interest, the investor has gained nothing in terms of buying power.

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The Formula:
\n\( (1 + i) = (1 + r)(1 + h) \)
\nWhere:
\n\( i \) = Nominal (money) interest rate
\n\( r \) = Real interest rate
\n\( h \) = Expected inflation rate

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Analogy: Imagine you lend a friend enough money to buy 100 apples. When they pay you back a year later, you want enough money to buy those 100 apples (inflation) PLUS a few extra apples as a "thank you" (real return).

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B. Government Monetary Policy

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Central banks (like the Bank of England or the Federal Reserve) use interest rates as a tool to control the economy.
\n- To stop high inflation: They raise interest rates (making borrowing expensive, which slows spending).
\n- To boost a weak economy: They lower interest rates (making borrowing cheap, which encourages spending).

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C. The Yield Curve (Term Structure of Interest Rates)

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The yield curve shows the relationship between the interest rate (yield) and the time until the debt is paid back (maturity). Usually, the longer you lend money, the higher the interest rate you demand.

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There are three theories why the curve is usually upward-sloping:

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  1. Expectations Theory: People think interest rates will rise in the future, so long-term rates are higher today.
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  2. Liquidity Preference Theory: Investors prefer to have cash "handy" (liquid). To persuade them to lock their money away for 10 years, you have to offer them a higher rate (a liquidity premium).
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  3. Market Segmentation Theory: Different borrowers and lenders stay in their "own lanes." Some only deal in short-term cash, others only in long-term mortgages. The rate in each "segment" is decided by its own supply and demand.
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Key Takeaway: Interest rates are driven by inflation expectations, government policy, and how long the money is being borrowed for.

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3. Quick Review & Common Pitfalls

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Common Mistakes to Avoid:
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- Mixing up PPPT and IRPT: Remember: PPP uses Prices (inflation). IRPT uses Interest Rates.
\n- The "Wrong Way" Math: When using the formulas, always double-check which currency is the "base" (\(i_b\)). If the rate is \(\$1.20 : £1\), the Pound is the base currency because there is only "one" of it.
- Real vs. Nominal: In the Fisher Effect, the Nominal rate is the one you actually see advertised at the bank. The Real rate is your actual profit after inflation.

Did You Know?

The "Big Mac Index" created by The Economist magazine is a famous (and fun) way of looking at Purchasing Power Parity. It compares the price of a McDonald's Big Mac in different countries to see if currencies are "undervalued" or "overvalued."

Summary Table for Risk Management Context:

Factor: Inflation
Impact: High inflation leads to a weaker currency (PPPT) and higher nominal interest rates (Fisher Effect).

Factor: Interest Rates
Impact: High interest rates lead to a forward discount on the currency (IRPT) and are often used by governments to fight inflation.

Don't worry if the formulas feel heavy right now! Practice a few calculations from your question bank, and you'll start to see the patterns. You've got this!