By Joan Wagner,2014-05-07 15:24
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We now look at Int'l. Parity Relationships, starting with the Law of One Price (LOP), extended to:

    Purchasing Power Parity (PPP) and Interest Rate Parity (IRP). These parity relationships help us to understand: 1) how ex-rates are determined, and 2) how to forecast ex-rates.

    Int'l. Parity is based on EMH (Efficient Market Hypothesis). FX/securities markets are efficient when:

    1) securities/FX are priced efficiently reflecting all currently available information, and 2) no arbitrage

    opportunities exist.

    Arbitrage: Riskless, certain profit opportunities by exploiting price discrepancies. Simultaneously

    buying and selling mispriced securities/FX to make a guaranteed, riskless profit without any

    investment. "Picking up dimes with a bulldozer." Example: triangular arbitrage. Int'l. parity conditions exist when there are no arbitrage opportunities and markets are in

    equilibrium. "No $100 bills lying on the sidewalk."

    Law of One Price (LOP): P

    = S ($/?) P, where D F

    P = Domestic Price ($) D

    P = Foreign Price (?) F

    S ($/?) = spot ex-rate.

Example: Gold in U.S. is $579.50/oz., gold in U.K. = ?305 and S= $1.9000/?

In USD: ?305 x $1.9000/? = $579.50, Gold is selling in both countries for the same price in USD

In BP: $579.50/oz. ? $1.9000 = ?305/oz, Gold is selling in both countries for the same price in BP

If Law of One Price (Price Equalization Principle) did not hold, arbitrage would be possible, and would

    quickly restore parity. For example, what if gold in U.K was $575? What if gold in US was ?300?


    IRP: No Arbitrage condition when int'l. financial markets (FX and money markets) are in

    equilibrium. Assuming free movement of capital, int'l. financial markets should be efficient. "Smell of

    profits" eliminates any discrepancies. Covered Interest Rate Parity = Parity conditions in fin. mkts., when forward markets are used to eliminate or "cover" any FX risk.

    Example: U.S. investor has $1 to invest for one year. You consider two strategies: 1) Invest in U.S.

    treasury securities at

    i, the domestic interest rate, for one year; or 2) Invest in foreign U.K. treasury $

    securities at i, and hedge FX risk by selling maturity value of ?s forward one year. ?

    In U.S., your payoff (maturity value) in one year will be: $1(1 + i) $

    - 1 -

    BUS 466/566: International Finance CH 6 Professor Mark J. Perry

In equilibrium this should be the same as your payoff in U.K.

    In U.K., your investment strategy involves:

    1. Sell $1 for ?s to get $1 ? S($/?) pounds. (We assume that S = S($/?)).

    2. Invest ?s at U.K. int. rate ( i) with payoff = $1/S x (1 + i) ??

    3. Sell ?s forward at F ($/?) for the maturity value of the UK investment, to get a guaranteed amount 360

    of $s.

    For either investment, you start and end with U.S. dollars. For Strategy #2, you have completely

    hedged ("covered") FX risk with the forward contract.

    The Interest Rate Parity (IRP) condition would be:

    (1 + i) = (F / S) (1 + i) $?

    IRP is an application of the Law of One Price (LOP) to financial securities, says that two identical

    securities (e.g. Treasury securities or bank CDs) should have the same return, after accounting for the

    ex-rates (S and F). We need the F rate here because we have added the time dimension, in this case

    one year into the future.

    Example: i= 5%; i = 8%; F = $1.4583/? and S = $1.50/? $ ?

    IRP Holds: (1.05) = ($1.4583 / $1.50) x 1.08

    Invest $1000 in U.S.: $1000 x 1.05 = $1050 in 1 year.

    Invest $1000 in U.K.: $1000 ? $1.50/? = ?666.6667 x 1.08 = ?720 x $1.4583333/? = $1050 in 1 year.

    One of the reasons IRP should hold is because of Covered Interest Arbitrage (CIA), no risk, no net

    investment arbitrage when IRP does not hold. Covered Interest Arbitrage (CIA) involves: 1) Borrow

    $s in U.S. at

    i, and buy UK pounds at S in spot market, 2) Invest (lend) in UK at i, 3) Sell pounds $?

    forward at F, to cover ex-rate risk. No investment, no risk arbitrage opportunities if IRP does not hold.

    See Example 6.1 (p. 135). i = 8% and i = 5%. S = $1.50/? and F = $1.48/?. IRP does not hold and ?$can be exploited by CIA.

    Logic: Nominal interest rates are 3% higher in U.K. (8%) than U.S.(5%). If IRP holds, what would we

    expect will happen to the ?? BP should depreciate by approx. 3% if IRP holds.

    %CHG = (F - S) / S x 100.

    ($1.50 - 1.48) / $1.50 x 100 = -1.333% (or use %CHG function on calculator)

    British Pound is expected to depreciate by only -1.33% instead of 3%, and is selling at a 1.33%

    discount in the forward market. Therefore, expected covered return in U.K. to a U.S. investor would be

    8% - 1.33% ? 6.667% (U.K.) vs. 5% (U.S.).

     - 2 -

    BUS 466/566: International Finance CH 6 Professor Mark J. Perry

Effective Return to U.S. Investor = i + % Appreciation Foreign Currency F

    Effective Return to U.S. Investor = i - % Depreciation Foreign Currency F

    Logic: When investing in a foreign market you are making 2 simultaneous investments: 1) the foreign security, and 2) the foreign currency.

We can also check IRP formula:

    1.05 ?=? (1.48/1.50) (1.08) = 1.0656

    1.05 < 1.0656

    5% < 6.56%

    Effective one-year return to a U.S. investor in U.K. (6.56%) is higher than return in U.S. (5%) by more than 1.5%.

    Arbitrage Strategy:

    1. Borrow $1m in U.S. at 5%, promise to pay $1.05m back in one year.

    2) Buy $1m worth of BP in spot market at S($1.50/?) for ?666,667 ($1m ? $1.50/?).

    3. Invest ?666,667 in U.K. at 8% to get guaranteed ?720,000 payoff in one year (?666,667 x 1.08).

    4. Enter into a 1 yr. forward contract to sell ?720,000s forward at $1.48/?, for $1,065,600 guaranteed in one year (?720,000 x $1.48/?).

    5. Pay back $1,050,000 on the loan in U.S., and make $15,600 arbitrage profit.

No risk, no investment, arbitrage strategy, see CF diagram, p. 136, Exhibit 6.2.

What will happen over time?

    1. Int. rates will ____ in U.S. due to borrowing pressure. Demand for Credit goes up.

    2. Int. rates will ____ in U.K. due to buying pressure for bonds. Bond prices rise, int. rates fall. 3. ? will _________ in spot market due to buying pressure, S will rise.

    4. ? will _________ in the forward market, due to selling pressure, F will fall.

    The difference between the two int. rates (3%) will narrow, and the difference between the S and F will widen (the forward discount for ? will increase from 1.33%), until IRP is restored, possibly at a

    forward discount of 2% for the ?, until the int. rate spread is EXACTLY equal to the %CHG in ?. For example, suppose interest rates end up around 5.5% in U.S. and 7.5% in U.K., and the ? sells at a

    forward discount of 2% in the Forward Mkt. (S = $1.505, F = $1.4749). In that case, your effective

    return is about 5.5% in EITHER country, and IRP is restored, partly by: a) a decrease in the interest rate differential and partly by: b) an increase in the forward premium.

    Another way to view IRP:


     ? i + (F - S) / S $?

     (i - i) ? (F - S) / S (Forward discount or premium for the ?) $?

    - 3 - BUS 466/566: International Finance CH 6 Professor Mark J. Perry

Shows that int. rates (bond prices) are directly linked to S and F ex-rates, and says that the difference in

    interest rates should be equal to the forward discount or premium for FX.

    The above equality can be represented graphically, IRP line on page 136 (Exhibit 6.3). Note: Units for

    both axes are %.

    Point A represents the previous example. Int. rates are 3% higher in U.K. than U.S., so that the

    ? should depreciate by 3% and be selling at a 3% forward discount according to IRP, however it is

    actually selling at a 1.33% forward discount, representing profit opportunities in U.K. Anything above

    the IRP line represents profits by either: a) investing in U.K. instead of U.S., or by b) borrowing in U.S.

    and lending in UK (arbitrage).

    Anything below the IRP line represents profit opportunities by either: a) investing in U.S., or b)

    borrowing in U.K. and lending in U.S. Point B: U.S. interest rates are 4% higher than U.K., so U.S.

    dollar should depreciate by 4% and pound appreciate by 4%. However, if the dollar was actually

    selling at a 2% discount (pound at 2% premium) in the forward market, U.S. investment would be very

    attractive. You could borrow in U.K., invest in U.S. and make money.

    See CIA Example 6.2 (p. 137) for a 3-month period using interest rates in Germany and the ?. Interest

    rates are usually quoted at annual rates, so an adjustment must be made. Also, IRP formula (6.1) is

    based on American terms ($1.50/?), and the ? is quoted here in European terms (?/$).

    3-month Interest Rates: i

     = 2% (U.S. based on 8% annual) and i = 1.25% (Germany based on 5%) $?

    Convert ex-rates on p. 137 to American terms to check IRP:

    S = $1.250/? and F = $1.2510/?, dollar selling at 3

    1.02 ?=? (1.2510/1.250) (1.0125)

    IRP: 1.02 > 1.0133, 3-month return is higher in U.S. than Germany. Strategy: Invest in US, or use

    CIA by borrowing in Germany, and invest in U.S. to make money.

    According to the difference in interest rates (0.75%), the $ should be selling at a 3-month 0.75%

    forward discount for IRP to hold. However, the dollar is selling in the forward market at only about a

    0.08% discount [(F - S) / S]. A German investor can get 1.25% yield in Germany vs. a 2% - .08% =

    1.92% in the U.S., starting by converting euros for dollars, investing in U.S. at 2%, and selling the $s

    forward at F

     to get ?s back in 3 months (start and end with euros). 3


    1. Borrow ?800,000 (equal to $1m) in Germany @ 1.25%, promise to pay ?810,000 in 3 months.

    2. Sell ?800,000 for $ at $1.2500/? = $1m

    3. Invest $1m for three months in U.S. @ 2% to get $1,020,000 in three months.

    4. Sell $1,020,000 forward @ $1.2510/? = ?815,347.7218 ($1,020,000 ? $1.2510) 5. Pay back loan of ?810,000 and end up with ?5,347.7218 arbitrage profit (or $6690 @ F = $1.2510, ?5,347.7218 x $1.2510/?).

     - 4 - BUS 466/566: International Finance CH 6 Professor Mark J. Perry

Note: This would represent a point below the line on Exhibit 5.3. Adjustment would take place by a

    decrease in the interest rate differential and an increase in the forward discount for the dollar. Example:

    i = 1.75% and i = 1.50%, and $ (?) sells at forward discount (premium) of .25%. German investor $?

    gets effective return of 1.5% in either country, U.S. investor gets 1.75% effective return in either


US: 1.75% - .25% = 1.50%, same as 1.50% in Germany


IRP helps explain ex-rate determination, by linking interest rates and ex-rates. We can rearrange the

    IRP formula:

S ($/?) = (1 + i

    ) x F ?

     (1 + i) $

    Spot ex-rates ($/?) are partly determined by relative interest rates, i.e., the interest rate in U.K. (and

    other countries) relative to interest rates in U.S. From the formula above, we can see that if interest

    rates increase in the U.K. (U.S.), the ? ($) will appreciate (holding F constant) as capital flows to the

    countries where interest rates are increasing, especially if the real interest rate is increasing.

    Forward rates also influence ex-rates. We can express F as: t+1

    F= E (S | I ) t+1 t+1t

    which says that the Forward Rate (F) is the Expected (E) future Spot Rate when the forward contract t+1matures in the future at time t+1, conditional upon all current and relevant information now, at time t

    (I). What relevant information?? t

    Combining the two equations above, we have:

    S = (1 + i) x E (S | I ) t?t+1t

     (1 + i) $

    We conclude that: 1) Expectations about the future spot rate, influence today's spot rate. If the

    expected spot rate goes up, the current spot rate (S) goes up now. Expectations drive the spot and

    forward rates.

    2) Information (I) drives ex-rates. Information changes daily, and forward and spot rates change daily

    as information changes. Ex-rates are dynamic and volatile. EMH says that prices (ex-rates) reflect

    ALL currently available information, and the only thing that changes prices is NEW information.

    Conclusion: Expectations and Information are important determinants of ex-rates, Spot and Forward

    markets, which are extremely dynamic markets.

     - 5 - BUS 466/566: International Finance CH 6 Professor Mark J. Perry

    We can also say that: (i - i) = E(e), $?where E(e) is the expected rate of change in S, or the expected percentage (%) change. The relative

    interest rate differential between two countries should reflect the expected percentage change in S. If

    one-year interest rates are 3% higher (lower) in UK, we expect the Pound to depreciate (appreciate) by


(5% - 8%) = -3% Interest rates are higher in U.K. than U.S., ? is expected to depreciate by 3% over yr.

(7% - 4%) = +3% Interest rates are higher in U.S., ? is expected to appreciate by 3% over the year.

Current example using current market data (9/24/06): Does IRP currently hold?

S = $1.2788 / ?


     = $1.2984 / ? 360

    LIBOR = 5.31% (1-year rate for USD)

    EURIBOR = 3.725% (1-year rate for Euros)

Calculation for IRP:


Although it should and does hold most of the time, why might IRP not always hold exactly, i.e. how to

    explain deviations from IRP.

    1. Transaction costs. We have so far assumed that transaction costs = 0. Deviations from IRP could be explained by transaction costs. For example, a) the borrowing and lending interest rate are NOT

    usually the same, as we assumed in the previous examples of CIA. Interest rates are usually higher for

    borrowing than for lending, e.g., commercial banks. Therefore, higher interest rates for borrowing may

    eliminate or exceed any potential arbitrage profits.

b) Also, there are transaction costs (commissions, bid-ask spreads, fees, etc.) to buy/sell currency and

    forward contracts and securities (bank CDs), which we have ignored, these may reduce or eliminate

    arbitrage profits.

    Therefore, the IRP line should have a band around it to reflect transactions costs, see Exhibit 5.4, p.

    139. Deviations within the shaded area (Point D) do not represent arbitrage opportunities, only deviations outside the shaded area (Point C).

    2. Capital controls that limit, restrict or ban cross border capital flows (in or out of a country), can create significant barriers to intl. arbitrage, resulting in possible deviations from IRP. See Japan story

    on pages 140-141. Between 1978-1979, Japan restricted capital inflows to prevent Yen from

BUS 466/566: International Finance CH 6 Professor Mark J. Perry - 6 -

appreciating. Why? Deviations from IRP resulted in 1978 and 1979, but did not reflect unexploited

    arbitrage opportunities. See Exhibit 6.5 on p. 140.

    PURCHASING POWER PARITY (PPP) PPP is the Law of One Price (LOP) applied to a standard commodity basket.

    P= S x P $ ?

    where Pis the domestic price level (CPI), Pis the foreign price level (CPI), and S = $/? ex-rate. PPP $ ?

    says that the dollar price of the commodity basket in the U.S. should be equal to the dollar price of the

    same commodity basket purchased in U.K. PPP is the LOP applied to a standard commodity basket,

    which should be priced the same in all countries, when measured in a common currency. What if

    prices were higher on average in U.S. than in the U.K.?:

    P > S x P $ ?

    Commodities would be purchased in ____ and sold in the _____, which would put upward pressure on:

    a) the _____ (S goes up) and b) _____ prices (go up), restoring PPP.

    Or we can also say:

    S = P $

     P ?

    where the spot rate (S) is the ratio between the two country's price levels. If domestic U.S. prices rise

    (P goes up), S should go up, meaning that the _____ is appreciating and the ____ is depreciating. . $

    Q: What would cause U.S. prices to be rising?

    Absolute PPP links ex-rates to the relative price levels (P) in two countries

    Relative PPP looks at Relative Inflation Rates (%): e = %INF - %INF , usF

    where e is the % change in the ex-rate.

    If INF > INF, then the dollar will depreciate and the pound will appreciate (S will get bigger and e usF

    will be positive).

    If INF < INF, then the dollar will appreciate and the pound will depreciate (S will get smaller, and usF

    e will be negative).

Therefore, ex-rates are linked to relative prices and relative inflation rates. If annual inflation in the

    U.S. is 6% and only 4% in U.K., then the dollar should depreciate by 2% annually and the pound will BUS 466/566: International Finance CH 6 Professor Mark J. Perry

    - 7 -

appreciate by 2%. If inflation in the U.S. is 6% and 9% in U.K., the pound should depreciate by 3%

    and the dollar should appreciate by 3%.

Whichever country has the higher (lower) inflation rate will experience a currency depreciation


BIG MAC PPP, see p. 142-143, annual report by The Economist to test for PPP/LOP. If LOP holds,

    the price of a Big Mac should sell for the same price around the world, measured in dollars using the

    actual spot ex-rate. Procedure: Big Mac sells for $2.49 in U.S., take $2.49 to countries around the

    world, convert $2.49 to local currency, and go buy a Big Mac. If Big Macs are cheap (expensive), the

    dollar is overvalued (undervalued), according to PPP or LOP.

Example: Take $2.49 to Argentina, convert to 7.79 pesos ($2.49 x pesos3.13/$), compare 7.79 pesos to

    Big Mac price in pesos: only 2.50 pesos, so you could buy 3 Big Macs, dollar (peso) is overvalued

    (undervalued) by 68%. Take $2.49 to Switzerland, convert to SF4.134 (2.49 x 1.66), compare to Big

    Mac price of SF6.30, dollar is undervalued by +53% (4.134 vs. 6.30).


    e = %INF

     - %INF, or usF

    (INF - INF) - e = 0 if PPP holds USF

    When PPP does NOT hold, the real, effective exchange rate changes, and affects a country’s

    international competitiveness and trade balance.

    The real, effective exchange-rate for the USD rises IF US inflation (5%) exceeds inflation abroad

    (3.5%), and the dollar doesn’t depreciate by the full inflation differential of 1.5%. In that case, the real,

    effective ex-rate value of the USD has risen, making the U.S. exports less competitive.

    The real, effective exchange-rate for the USD falls IF US inflation (5%) exceeds inflation abroad

    (3.5%), and the dollar depreciates by more than the full inflation differential of 1.5%. In that case, the

    real, effective ex-rate value of the USD has fallen, making the U.S. more competitive.

    Example: Inflation in U.S. is 5%, inflation in U.K. is 3.5%, we would expect e = +1.5%. The dollar

    should depreciate by 1.5% and the pound should appreciate by 1.5%, according to PPP. If the dollar

    actually depreciates by more than 1.5%, i.e., by more than predicted by PPP, it strengthens the

    competitiveness of U.S. industries in world markets (below line in Exhibit 6.6 on p. 145) because the

    “real, effective exchange rate” has fallen. On the other hand, if the dollar depreciates by less than 1.5%,

    the real, effective ex-rate rises, making the US less competitive.

    Or, assume that U.S. inflation is 2% and U.K. inflation is 5%, and the dollar is expected to appreciate

    by +3%. If dollar actually appreciates by more than 3%, it weakens our competitiveness in world

    markets (mid-1980s), because the real, effective exchange rate has increased. If the dollar appreciates

    by less than the full 3%, the real, effective ex-rate decreases, making the US more competitive.

     - 8 - BUS 466/566: International Finance CH 6 Professor Mark J. Perry

Exhibit 6.6 shows that ex-rates (indexes) often deviate from PPP, and are often above and below the

    rate predicted by PPP. Example: US dollar was much stronger in mid-1980s than justified by PPP. Our inflation rate was not that much lower than other countries, and the $ still got much stronger

    than PPP would explain. (Appreciation of the dollar was not explained by low U.S. inflation compared

    to inflation in other countries, see example above.) During this period, U.S. manufacturers and

    exporters were complaining that the dollar was too strong, their products were not competitive globally.

    Why doesn’t PPP always hold?

    PPP is just the LOP extended to a standard commodity basket. For PPP to hold, the commodity basket

    would have to be: a) consistent across countries, b) all goods in basket would have to be tradable so

    that arbitrage would be possible, and c) prices would have to be perfectly flexible (no price controls).

    Not all of these conditions are met, so PPP does not always hold. For example, see world prices in

    Exhibit 6.7 on p. 146. The standard CPI commodity basket is not the same in U.S. vs. Japan vs. U.K.,

    and not all goods are tradable (e.g. haircuts) and not all prices are perfectly flexible. Also, there are

    transportation costs, transactions and possible trade barriers (tariffs, quotas) that would prevent PPP

    from strictly holding.

    PPP would hold with "frictionless trading." Holds most closely with homogenous, traded commodities,

    (Treasury bills, gold, oil, wheat, steel, bank CDs, etc.)


    1. More of a long run condition than short run.

    2. Can be used to tell if a currency is over or under-valued.

    3. Int'l. comparisons are more accurate using PPP-ex-rates vs. mkt ex-rates. See Exhibit 6.8 page 147.

    To compare GDP across countries, we have to convert to a common currency, like dollars. However

    using market rates can distort the comparison. If the dollar (pound) is under/over valued, then

    converting into dollars may be distorted.

    For example, according to PPP, China's currency is artificially undervalued (and $ is artificially

    overvalued) at the market ex-rate, lowering the value of China's GDP in the first column ($1.41T),

    ranking 7th. Adjusting for PPP value of China's currency, they are second ($6.43T). India and Brazil

    also rise in the rankings because their currencies are undervalued according to PPP, and Japan,

    Germany, France, U.K. and Italy fall. The ? and ? are OVERVALUED according to PPP. Also, prices

    are cheaper in China and India than in U.S. for the same goods and services, which distorts

    international comparisons at market ex-rates.


    Nominal Int Rate

    ei = r (real rate) + Π (Expected inflation) Fisher Equation (p. 147) us

    Example: One-year nominal interest rates in U.S. are 5%, the one-year real rate (ρ) is 2%, and the one-

    year expected rate of U.S. inflation is 3%. This would hold for other countries as well.

    BUS 466/566: International Finance CH 6 Professor Mark J. Perry

    - 9 -

    If the real interest rate (r) is constant, changes in nominal interest rates reflect changes in expected einflation (Δi = ΔП). Fisher Effect: One-to-one relationship between changes in inflation expectations and changes in nominal interest rates. Assume that the real interest rate is the same internationally, due

    to free capital flows. In that case the relative difference in nominal interest rates reflects relative

    differences in expected inflation:

    Fisher Effect:

    (i - i) = E - П) $?$?

    Assuming a constant real interest rate (r), the differences in nominal interest rates between US and UK

    reflect differences in expected inflation between U.S. and U.K.

    With unrestricted capital flows, we can assume that the real rate of interest is constant internationally.

    We would have the following additional parity conditions (see page 148):

International Fisher Effect (IFE):

E (e) ? ( i

     - i ) $?

    The difference in nominal interest rates (i - i) between U.S. and U.K. reflects the expected change in $?the ex-rate. For a one year period, if i = 5% and i= 7%, the dollar (pound) is expected to appreciate $? (depreciate) by 2% over the next year. If i = 5% and i= 4%, the pound (dollar) is expected to $? appreciate (depreciate) by 1% over the next year.

    Forward Expectations Parity (FEP): (F - S) / S = E (e)

    Any forward premium or discount will be equal to the expected change in the ex-rate. If the pound is

    expected to depreciate (appreciate) by 2% over the next year, it will be priced at a 2% forward discount

    (premium) in the forward market.


    See Exhibit 6.9, p. 148: The difference in nominal interest rates (%) reflects the difference in inflation

    rates (%), which is also equal to the expected change in S (%) or E (e), which is also reflected in the

    forward premium or discount (%) or (F S) / S.

EXAMPLE 1: If one-year T-bills = 8% in U.S. and 6% in U.K., the +2% difference reflects the

    expectation of 2% higher inflation in U.S. In addition, the BP (USD) is expected to appreciate

    (depreciate) by +2%, which is reflected in a forward premium (discount) of +2% for the BP (USD).

    EXAMPLE 2: Assume that real rate r = 2%, Expected inflation is 2% in U.S. and 4% in

    U.K. Nominal interest rates will be 6% in U.K. and 4% in the U.S. for one-year T-bills, and (i

     - i) = $?

     - 10 - BUS 466/566: International Finance CH 6 Professor Mark J. Perry

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