Source: ECO 201, University of Florida
Tags: exchange rate, nominal exchange rate, real exchange rate, no round trip profit, no arbitrage, purchasing power parity, floating exchange rate, fixed exchange rate, managed float, currency peg, balance of payments, current account, capital account, financial account, net exporter, net importer, net borrower, net lender
Difficulty: Intermediate Prerequisites: Understanding of money supply and monetary policy tools (see Part 2 of these notes). Familiarity with supply and demand in the context of asset markets is helpful.
This section ties domestic monetary policy to the rest of the world. Exchange rates determine how much one currency is worth in terms of another, which affects trade, investment flows, and the price of imports and exports. The balance of payments is the accounting framework that tracks all economic transactions between a country and the rest of the world. If you have missed recent lectures, the main idea is that money flows across borders for two reasons: to buy goods and services (captured in the current account) and to buy assets (captured in the financial account). Exchange rates adjust to keep these flows in balance.
Exchange rates are determined by supply and demand for currencies and are influenced in the short run by interest rate differentials and expectations. The "no round trip profit" condition prevents riskless arbitrage across currency pairs. Countries choose different exchange rate regimes (floating, fixed, managed). The balance of payments report tracks a country's transactions with the world, and its two main accounts (current and financial) must sum to zero.
Exchange rate
The price of one currency expressed in terms of another. For example, if £1 = $1.25, the exchange rate of the pound in dollar terms is 1.25. Think of it as the "price" of money itself.
Nominal exchange rate
The rate at which one currency trades for another in the foreign exchange market, unadjusted for price levels. This is the number you see at the bureau de change.
Real exchange rate
The nominal exchange rate adjusted for differences in price levels between two countries. It measures the rate at which you can trade the goods and services of one country for those of another. In simple terms, it tells you how far your money actually goes abroad after accounting for local prices.
Appreciation
An increase in the value of a currency relative to another. If the pound goes from $1.25 to $1.30, the pound has appreciated (and the dollar has depreciated).
Depreciation
A decrease in the value of a currency relative to another. Makes exports cheaper and imports more expensive for the home country.
No round trip profit (no-arbitrage condition)
The principle that you cannot make a riskless profit by converting currency A to B to C and back to A. If such a profit existed, arbitrageurs would exploit it until exchange rates adjusted to eliminate it. Think of it as the foreign exchange market's self-correcting mechanism against free money.
Purchasing power parity (PPP)
The theory that, in the long run, exchange rates adjust so that identical goods cost the same in different countries when priced in a common currency. In simple terms, a basket of groceries should cost roughly the same in London and New York once you convert currencies. Holds loosely in the long run, poorly in the short run.
Floating (flexible) exchange rate
An exchange rate regime in which the currency's value is determined entirely by market supply and demand, with no government intervention. The US dollar, euro, and British pound all float.
Fixed (pegged) exchange rate
An exchange rate regime in which the government or central bank commits to maintaining the currency at a specific value relative to another currency or basket. The central bank buys or sells its own currency to hold the peg.
Managed float (dirty float)
A hybrid regime in which the exchange rate is primarily market-determined, but the central bank intervenes occasionally to smooth large fluctuations or steer the rate.
Balance of payments (BoP)
A comprehensive record of all economic transactions between residents of a country and the rest of the world over a period (usually a year or quarter). The BoP always balances in an accounting sense.
Current account
The BoP component that records trade in goods and services, income flows (wages and investment income), and unilateral transfers (foreign aid, remittances). A current account surplus means the country earns more from the rest of the world than it spends; a deficit means the opposite.
Financial account (capital and financial account)
The BoP component that records purchases and sales of financial assets (stocks, bonds, direct investment, bank deposits) between domestic and foreign residents. A financial account surplus (net capital inflow) means foreigners are buying more of the country's assets than the country's residents are buying abroad.
Net exporter
A country whose exports of goods and services exceed its imports, resulting in a current account surplus (or at least a trade surplus).
Net importer
A country whose imports of goods and services exceed its exports, resulting in a current account deficit (or trade deficit).
Net lender
A country that lends more to the rest of the world than it borrows, corresponding to a financial account deficit (net capital outflow). Net lenders typically run current account surpluses.
Net borrower
A country that borrows more from the rest of the world than it lends, corresponding to a financial account surplus (net capital inflow). Net borrowers typically run current account deficits.
An exchange rate is simply the price of one currency in terms of another. Like any price, it is determined by supply and demand.
Demand for a currency comes from:
Foreigners wanting to buy a country's exports (they need the local currency to pay)
Foreign investors wanting to buy the country's assets (bonds, stocks, real estate)
Speculators expecting the currency to appreciate
Supply of a currency comes from:
Domestic residents wanting to buy imports (they sell local currency to get foreign currency)
Domestic investors wanting to buy foreign assets
Speculators expecting the currency to depreciate
This condition states that converting currencies in a loop cannot yield a riskless profit.
Example with three currencies: Suppose £1 = $1.50, $1 = ¥100, and £1 = ¥150.
Start with £1. Convert to dollars: $1.50.
Convert $1.50 to yen: 150 yen.
Convert 150 yen back to pounds: £1.
No profit. The cross rates are consistent.
If the yen/pound rate were ¥160 instead: starting with £1, you would end up with £1.067 after the round trip, a riskless profit of 6.7%. Arbitrageurs would immediately exploit this, buying pounds with yen, which would drive the yen/pound rate back toward 150 until no profit remained.
This condition implies that cross rates must be consistent. If you know two exchange rates, the third is determined.
Formula: e(A/C) = e(A/B) × e(B/C)
Where e(A/B) is the price of currency B in terms of currency A.
In the short run, exchange rates are driven primarily by:
Interest rate differentials: If Country A raises its interest rate relative to Country B, investors move funds to A to earn higher returns. Demand for A's currency rises, and it appreciates. This is the most important short-run factor.
Expectations about future exchange rates: If investors expect a currency to appreciate, they buy it now, causing it to appreciate immediately (a self-fulfilling element).
Changes in risk perception: If a country's economy looks unstable, investors pull out, causing depreciation.
Relative inflation rates: Higher inflation in one country reduces demand for its currency (its goods become more expensive), causing depreciation.
In the short run, financial flows (the financial account) dominate exchange rate determination because the volume of currency trading for financial investment dwarfs the volume for trade in goods and services.
Floating (flexible) exchange rate:
The currency's value is set by market forces.
Advantages: automatic adjustment to trade imbalances; monetary policy remains independent (the central bank can set interest rates for domestic goals).
Disadvantages: exchange rate volatility can create uncertainty for international trade and investment.
Fixed (pegged) exchange rate:
The central bank commits to a specific exchange rate and intervenes to maintain it.
To prevent depreciation: the central bank sells foreign reserves and buys its own currency (reducing supply of domestic currency in the market).
To prevent appreciation: the central bank buys foreign currency and sells its own (increasing supply of domestic currency).
Advantages: price stability in international trade; reduces exchange rate risk.
Disadvantages: the central bank must hold large foreign reserves; monetary policy independence is sacrificed (it must set interest rates to defend the peg, not to manage domestic inflation or employment).
Managed float (dirty float):
Primarily market-determined, but the central bank intervenes when it judges fluctuations are excessive or destabilising.
Most real-world regimes fall somewhere on this spectrum rather than being purely floating or purely fixed.
The BoP records all transactions between a country's residents and the rest of the world.
It has two main accounts:
Current account: Trade in goods, trade in services, income receipts and payments (wages, investment income), and unilateral transfers.
Financial account: Net acquisition of financial assets abroad and net incurrence of liabilities to foreigners.
There is also a small capital account (covering non-financial assets like patents, debt forgiveness), but it is typically negligible in exam contexts.
Key identity: Current account + Financial account + Capital account = 0
In practice, a statistical discrepancy line adjusts for measurement errors, but conceptually the accounts must balance. A current account deficit must be financed by a financial account surplus (net capital inflow), and vice versa.
Look at the current account balance (or more narrowly, the trade balance in goods and services).
Current account surplus (or trade surplus) = net exporter. The country sells more to the world than it buys.
Current account deficit (or trade deficit) = net importer. The country buys more from the world than it sells.
Look at the financial account balance.
Financial account surplus (net capital inflow) = net borrower. More foreign money is flowing into the country (foreigners buying the country's assets/lending to it) than the country is sending abroad.
Financial account deficit (net capital outflow) = net lender. The country's residents are investing more abroad than foreigners are investing domestically.
Because the BoP must balance, a net importer is generally a net borrower (it finances its trade deficit by borrowing from abroad), and a net exporter is generally a net lender.
Formula | Expression | Notes |
|---|---|---|
Cross rate consistency | e(A/C) = e(A/B) × e(B/C) | No round trip profit condition |
Real exchange rate | RER = (Nominal rate × Domestic price level) / Foreign price level | Measures competitiveness |
BoP identity | Current account + Financial account + Capital account = 0 | Must balance by definition |
When the US runs a large trade deficit (net importer), it is simultaneously a net borrower: countries like China and Japan buy US Treasury bonds to recycle their export earnings. This is the BoP identity in action.
The no-round-trip-profit condition is enforced in real time by algorithmic traders in the foreign exchange market. Discrepancies are exploited within milliseconds, which is why the condition holds almost perfectly in practice.
"A current account deficit is bad." A deficit means the country is importing more than it exports, but it also means foreign capital is flowing in (financial account surplus). That inflow funds investment that can boost future growth. Whether a deficit is "good" or "bad" depends on what the borrowed funds are used for.
"Fixed exchange rates are more stable than floating rates." Fixed rates prevent day-to-day fluctuations, but they can lead to sudden, large devaluations when the peg becomes unsustainable (as in the 1997 Asian financial crisis). Floating rates adjust gradually.
"Purchasing power parity holds at all times." PPP is a long-run tendency, not a short-run prediction. Transport costs, tariffs, non-traded goods, and differences in product quality mean that identical goods rarely cost exactly the same across countries.
"A country can be a net exporter and a net borrower at the same time." This is extremely unusual. The BoP identity means a current account surplus (net exporter) is paired with a financial account deficit (net lender), not net borrowing.
⚠️ The no-round-trip-profit condition is a common calculation question. Given two exchange rates, you may be asked to find the third consistent cross rate, or to identify whether an arbitrage opportunity exists.
⚠️ Know the components of the current account and financial account. Be able to classify a given transaction (e.g. "a US firm buys a factory in Mexico" goes in the financial account).
⚠️ Be prepared to determine whether a country is a net exporter/importer and net borrower/lender from BoP data. This is a straightforward reading-comprehension exercise if you know where to look.
⚠️ Understand the trade-offs between fixed and floating exchange rate regimes, particularly the loss of monetary policy independence under a fixed rate.
⚠️ Short-run exchange rate movements driven by interest rate differentials are frequently tested. If Country A raises rates, its currency appreciates. Know why.
True or False: A current account deficit means a country is a net exporter.
Fill in the blank: The no-round-trip-profit condition ensures that ______ rates are consistent across currency pairs.
True or False: Under a fixed exchange rate regime, the central bank has full independence to set interest rates for domestic goals.
Fill in the blank: If a country has a financial account surplus, it is a net ______.
True or False: In the short run, interest rate differentials are the primary driver of exchange rate movements.
Answers: 1. False (a deficit means net importer). 2. Cross (exchange). 3. False (it must set rates to defend the peg). 4. Borrower. 5. True.
Q: Explain the no-round-trip-profit condition using a numerical example.
A: Suppose $1 = €0.90 and €1 = ¥130. The consistent dollar/yen rate must be 0.90 × 130 = ¥117 per dollar. If the actual rate were ¥120 per dollar, you could start with $1, convert to yen ($1 = ¥120), convert yen to euros (¥120 / 130 = €0.923), convert euros to dollars (€0.923 / 0.90 = $1.026), netting a riskless 2.6% profit. Arbitrageurs would exploit this until the rates adjusted to eliminate the discrepancy.
Q: A country has the following BoP data: exports of goods $500bn, imports of goods $700bn, net services +$50bn, net income +$20bn, net transfers -$30bn. What is the current account balance? Is the country a net exporter or net importer?
A: Trade balance in goods = $500bn - $700bn = -$200bn. Current account = -$200bn + $50bn + $20bn - $30bn = -$160bn. The country has a current account deficit, so it is a net importer.
Q: Using the BoP identity, what must the financial account balance be for the country above (ignoring the capital account)?
A: The financial account must show a surplus of +$160bn (net capital inflow) to offset the current account deficit. The country is a net borrower.
Q: Why does a country with a fixed exchange rate lose monetary policy independence?
A: To maintain the peg, the central bank must buy or sell foreign reserves whenever market pressure pushes the exchange rate away from the target. If the domestic currency faces depreciation pressure, the central bank must sell foreign reserves and effectively tighten monetary conditions, even if the domestic economy needs lower interest rates. The peg dictates the central bank's actions, leaving no room to set policy for domestic objectives.
Q: What causes a currency to appreciate in the short run?
A: The most common cause is a rise in domestic interest rates relative to foreign rates. Higher returns attract foreign capital inflows, increasing demand for the domestic currency. Other factors include expectations of future appreciation, reduced political or economic risk, and lower inflation relative to trading partners.
Exchange rate movements feed back into the AD-AS model from Part 1. A depreciation makes exports cheaper and imports more expensive, shifting AD to the right (increasing net exports). An appreciation does the opposite.
The loss of monetary policy independence under fixed rates connects to the "impossible trinity" or trilemma: a country cannot simultaneously have a fixed exchange rate, free capital flows, and independent monetary policy. This is a topic some courses cover in more advanced sections.
The balance of payments links directly to the loanable funds market: a current account deficit means the country is borrowing from abroad, which appears as foreign capital entering the domestic loanable funds market.
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