CFA Level II Exam · Currency Exchange Rates: Understanding Equilibrium Value

Balance of Payments and Exchange Rates for CFA Level II

Q: How do current account deficits affect currency value?

A deficit means the country must attract capital inflows to fund it. If the funding is stable and long-term, the currency can hold up. If inflows slow or reverse, the currency tends to depreciate.

Q: What is the Mundell-Fleming model in CFA Level II?

It shows how monetary and fiscal policy affect exchange rates in an open economy, depending on capital mobility. With high mobility under floating rates, fiscal expansion appreciates the currency and monetary expansion depreciates it. With low mobility, trade effects dominate and expansion tends to depreciate the currency.

Q: What is the portfolio balance approach?

It treats exchange rates as the result of investors adjusting their holdings of domestic and foreign assets. Persistent government deficits increase the supply of domestic debt, and investors may require a lower currency price or higher returns to hold it. This can weaken the currency over the long run.

Q: What is the Marshall-Lerner condition?

It says depreciation improves the trade balance only if the sum of the absolute values of export and import demand elasticities exceeds 1. In the short run the J-curve effect can still make the balance worse first.

Updated 7 October 2026 · Fact-checked

The balance of payments records a country's trade and financial flows with the world. Current account deficits must be financed by capital inflows. If investors stop funding the gap, the currency tends to fall. To solve questions, identify the flow, its direction, and whether the model is Mundell-Fleming or portfolio balance.

Understand Balance of Payments and Exchange Rates

The balance of payments (BOP) is a record of all transactions between a country's residents and the rest of the world. It has three parts: the current account (trade in goods and services, income, transfers), the capital account (small items such as debt forgiveness and transfers of non-produced assets), and the financial account (purchases and sales of foreign assets, direct and portfolio investment). In principle, current account + capital account + financial account = 0. A current account deficit is matched by a net inflow in the financial account.

This identity is why a deficit is not automatically bad for a currency. A country that imports more than it exports must borrow or sell assets to foreigners. If foreigners are happy to buy its bonds, equities or property, the currency can stay strong. The danger comes when the deficit is large, the funding is short-term or fickle, and sentiment turns. Then capital inflows slow, and the currency must fall to restore balance.

There are two channels from a deficit to the exchange rate. The flow channel: a deficit means net supply of domestic currency to buy foreign goods, which pushes the currency down, and a weaker currency should in time help exports and cut imports. This correction can be slow or weak if the Marshall-Lerner condition fails (the sum of the absolute import and export demand elasticities must exceed 1 for depreciation to improve the trade balance), and in the short run the J-curve can make the balance worse before it improves. The financing channel: the deficit must be funded, and the cost and willingness of funding drive the currency.

The Mundell-Fleming model looks at how monetary and fiscal policy affect the exchange rate in an open economy, depending on capital mobility. With high capital mobility and floating rates, expansionary monetary policy lowers interest rates, causes capital outflow, and depreciates the currency. Expansionary fiscal policy raises interest rates, attracts capital, and appreciates the currency. If both policies are expansionary under high capital mobility, the combined effect is ambiguous.

With low capital mobility, trade effects dominate: expansionary fiscal policy raises income and imports, so the currency depreciates, while expansionary monetary policy depreciates it through both lower rates and higher imports. If both policies are expansionary under low capital mobility, both push the currency down, so the currency depreciates and the result is not ambiguous.

A quick summary: the mix of policy and capital mobility decides the sign. Fiscal expansion with high mobility gives appreciation. Fiscal expansion with low mobility gives depreciation. Monetary expansion gives depreciation in both cases. Only the combined expansionary mix is ambiguous, and only under high mobility.

The portfolio balance approach focuses on stocks rather than flows. Foreign investors hold domestic assets as part of diversified portfolios. A persistent government deficit increases the supply of government debt. For investors to hold more of it, they need either higher returns or a lower currency price. So persistent fiscal deficits can lead to a long-run weaker currency as investors rebalance. Portfolio balance also notes that a currency can strengthen in the short run if a deficit is financed by foreign buyers, but investors eventually hold their desired mix, and further deficits weaken the currency. Related ideas: a country with a large current account surplus may see its currency appreciate, while a reserve currency may be insulated for long periods because the world wants to hold its assets.

Key formulas to remember

Balance of payments identity: Current account + Capital account + Financial account = 0; Changes in official reserves are part of the financial account. In practice, a statistical discrepancy (errors and omissions) is needed for the identity to sum to zero. A current account deficit means a net financial account inflow.
Current account and national saving: Current account balance = Private saving + Government saving − Investment = S − I; A deficit means domestic investment exceeds national saving. Equivalent form: CA = (X − M) + net income and transfers.
Marshall-Lerner condition: |ε_X| + |ε_M| > 1; ε_X and ε_M are the price elasticities of export and import demand. If true, depreciation improves the trade balance once volumes adjust.
Mundell-Fleming summary (floating rates, high capital mobility): Expansionary fiscal → domestic currency appreciates; Expansionary monetary → domestic currency depreciates; Both expansionary (or both restrictive) → ambiguous; When fiscal and monetary policy are both expansionary, or both restrictive, their effects on the currency work in opposite directions, so the net result is ambiguous under high capital mobility; look at which effect the vignette says is stronger.
Mundell-Fleming with low capital mobility: Expansionary fiscal → currency depreciates (higher imports); Expansionary monetary → currency depreciates; Both expansionary → currency depreciates; Trade effects dominate because capital flows respond little to interest rate changes. The combined expansionary mix is not ambiguous here.

How to solve Balance of Payments and Exchange Rates questions

Use this method for any BOP or exchange rate model question in an item set.

1Read the vignette for the facts that matter: current account position, how it is financed, interest rate moves, policy stance, and capital mobility.
2Classify each flow as current, capital or financial account, and note its direction (inflow or outflow of foreign currency).
3Decide what is being asked: a short-run effect (flows, interest rates) or a long-run effect (stocks, portfolio rebalancing, elasticities).
4Choose the model: Mundell-Fleming for policy effects under different capital mobility, portfolio balance for persistent deficits and asset holdings, Marshall-Lerner and J-curve for trade balance response.
5Trace the chain: policy or flow → interest rates or asset demand → capital flows → demand for domestic currency → exchange rate.
6State the direction of the currency move, then check it against the exact condition in the vignette (floating or fixed, high or low mobility).
7Eliminate answers that reverse a link in the chain, then select the option that matches your direction and reasoning.

Quickest way: Policy and mobility grid

When to use it: Use when the question gives a policy mix and asks which way the currency moves.

Mark the capital mobility: high or low.
Mark the policy: fiscal expansion, monetary expansion, or tightening.
High mobility: monetary expansion means depreciation, fiscal expansion means appreciation (interest rate effect dominates).
Low mobility: any expansion that raises income and imports means depreciation (trade effect dominates).
If both policies are expansionary, the combined effect is ambiguous only under high capital mobility, unless the vignette says which dominates. Under low capital mobility, the currency depreciates.
For a deficit question, ask: who is funding it, and is that funding stable? Stable long-term funding means little pressure; hot money means risk.

Common mistakes in Balance of Payments and Exchange Rates

Saying a current account deficit always weakens the currency.
Students focus on the flow channel only.
Fix: Remember the deficit is financed by capital inflows. A strong appetite for the country's assets can keep the currency firm for years.
Mixing up Mundell-Fleming results for fiscal expansion under high and low capital mobility.
The same policy has opposite effects, and the two cases are easy to confuse.
Fix: High mobility: higher rates attract capital, so appreciation. Low mobility: higher imports dominate, so depreciation.
Treating monetary expansion as ambiguous in Mundell-Fleming.
Students copy the ambiguity of the fiscal case.
Fix: Monetary expansion lowers rates and raises income, and both effects push the currency down. It depreciates in both mobility cases.
Assuming depreciation immediately fixes a trade deficit.
Ignoring volume adjustment lags and elasticities.
Fix: Check Marshall-Lerner. Also note the J-curve: the balance can worsen first because contracts are fixed and import prices rise before volumes adjust.
Confusing the portfolio balance approach with a pure flow model.
Both mention capital flows.
Fix: Portfolio balance is about investors adjusting holdings of domestic and foreign assets. Persistent deficits raise asset supply and push the currency lower in the long run.

Worked examples

Example 1

Vignette: Country A has a floating exchange rate and highly mobile capital. Its government announces a large increase in spending financed by bond issuance, while its central bank holds the policy rate steady. Q1: What is the likely effect on A's currency in the Mundell-Fleming model? Q2: How would the answer change if capital were barely mobile? Q3: What does the portfolio balance approach add if the deficits persist?

Show the solution

Q1: With high mobility, fiscal expansion raises interest rates (more bond supply, higher demand for funds). Higher rates attract foreign capital, so demand for A's currency rises. The currency appreciates.
Q2: With low mobility, capital does not respond much to higher rates. Higher income raises imports, so more domestic currency is supplied to buy foreign goods. The currency depreciates.
Q3: Persistent deficits add to the stock of government debt. Investors must be induced to hold more of it, which needs higher expected returns or a lower currency price. Over time the currency tends to weaken as investors rebalance.

Answer: Q1: Appreciation. Q2: Depreciation. Q3: Persistent deficits eventually pressure the currency lower as investors rebalance portfolios.

Example 2

Vignette: Country B runs a current account deficit of 4% of GDP. It is financed mainly by foreign direct investment in factories and long-term bonds held by pension funds. B's currency has been stable. Analyst Rao says that the deficit makes depreciation inevitable. Q1: Is Rao correct? Q2: What would make the currency vulnerable? Q3: If B's currency depreciates and import and export demand elasticities sum to 0.8, what happens to the trade balance in the short run and once volumes have adjusted?

Show the solution

Q1: A deficit equals a financial account inflow. The inflow here is stable, long-term funding (FDI and pension holdings). Stable funding means no forced depreciation. Rao is not correct.
Q2: The currency becomes vulnerable if funding shifts to short-term, volatile portfolio flows, or if investor sentiment turns and inflows slow or reverse. A larger deficit or rising risk premium would add pressure.
Q3: Marshall-Lerner requires the sum of elasticities to exceed 1. Here 0.8 < 1, so the condition fails. Once volumes have adjusted, depreciation worsens the trade balance. In the short run, the J-curve effect also worsens the balance, because import prices rise before volumes respond. So the trade balance worsens both in the short run and after volumes adjust.

Answer: Q1: No, stable long-term financing can sustain a deficit. Q2: Short-term, reversible capital flows or a loss of confidence. Q3: The Marshall-Lerner condition fails because 0.8 is less than 1, so depreciation worsens the trade balance both in the short run and after volumes adjust.

Exam tips

Always read whether the vignette says capital mobility is high or low. It reverses the fiscal result in Mundell-Fleming.
When a question asks about a current account deficit, look for how it is financed. Stable FDI is very different from short-term portfolio flows.
For Marshall-Lerner questions, add the two elasticities in absolute value and compare with 1. Do not average them.
Watch for time horizon words: 'short run' points to interest rates and flows, 'long run' points to portfolio balance and asset stocks.
If both fiscal and monetary policy are expansionary, expect the result to be ambiguous only under high capital mobility, unless the vignette says which effect dominates. Under low capital mobility, the currency depreciates.

Balance of Payments and Exchange Rates in other exams

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

Balance of Payments and Exchange Rates: frequently asked questions

How do current account deficits affect currency value?

A deficit means the country must attract capital inflows to fund it. If the funding is stable and long-term, the currency can hold up. If inflows slow or reverse, the currency tends to depreciate.

What is the Mundell-Fleming model in CFA Level II?

It shows how monetary and fiscal policy affect exchange rates in an open economy, depending on capital mobility. With high mobility under floating rates, fiscal expansion appreciates the currency and monetary expansion depreciates it. With low mobility, trade effects dominate and expansion tends to depreciate the currency.

What is the portfolio balance approach?

It treats exchange rates as the result of investors adjusting their holdings of domestic and foreign assets. Persistent government deficits increase the supply of domestic debt, and investors may require a lower currency price or higher returns to hold it. This can weaken the currency over the long run.

What is the Marshall-Lerner condition?

It says depreciation improves the trade balance only if the sum of the absolute values of export and import demand elasticities exceeds 1. In the short run the J-curve effect can still make the balance worse first.