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Models of Exchange
Rate Determination
Lecture 1
IME LIUC Nov-Dec. 2003
Exchange Rates Movements Show Some
Daily and monthly exchange rates are
highly unpredictable
Exchange rates of countries with high
inflation depreciate in the long run by about
the inflation rate differential
 The high variability of exchange rate in the
short run is not systematically related to
change in money supply
 Correlation between monthly changes in
the exchange rate and the current account
position is low
Do We Have “a” Theory to Explain
Exchange Rate Behaviors?
No, we have several theories that try
to explain empirical regularities:
– The PPP model,
– Mundell Fleming model,
– Monetary Model,
– …..
They all have limitations and
Exchange-Rate Forecasting is Difficult!
"There may be more forecasting of
exchange rates, with less success, than
almost any other economic variable.
Although measures such as real interestrate differentials, differential rates of
productivity gains, and chronic external
deficits are often employed to explain
exchange rate behavior, none has been
found to be consistently useful in
forecasting exchange rates even over
substantial periods of one or two years."
Alan Greenspan (July 2002)
The Dornbush’s model:
the “overshooting” model
Why is the model so famous?
What is the model about?
What is the evidence for and against the
Why is the model so famous?
Quoting from Rogoff
– The model is “elegant”: it is the beauty and
clarity of Dornbush’s analysis that has
made it so flexible and useful.
– The model is “path breaking”: it changed
our way of thinking about the exchange
Quoting from Krugman
“Rudi was, first of all, the economist who
brought international monetary economics into
the modern world. The workhorse of preDornbusch open-economy macro, the MundellFleming model, was a fine thing.. But it didn’t
capture the volatility of a floating-exchangerate world, the way currencies can soar or
plunge not because big things have already
happened, but because things are expected to
happen.. Rudi’s famous “overshooting” paper
changed it all…”
(NYT, July 26 2002)
What is the model about?
 Two relationships lie at the hart of
the model:
– The UIP: it 1  i *  Et (et 1  et )
– The money demand:
pt  nit 1  lyt
The model also assumes that:
– P fix in the short-run and flexible in the longrun
– output y is exogenous
– money is neutral in the long run, so that a
permanent rise in m leads a proportionate rise
in e and p, in the long run.
How does the overshooting work?
Hp: Unanticipated permanent increase in the money supply m.
Long run: The increase in m will imply a proportional increase in P
and given that the PPP holds also in e
in the short run:
m rises but the price level is temporarily fixed, then the
supply of real balances must rise as well.
To equilibrate the system, the demand for real balances must
rise. Since output is assumed fixed in the short run, i on domestic
currency bonds falls.
 According
to the UIP, it is possible for i to fall if and only if, over
the future life of the bond contract, the home currency is expected to
But how is this possible if we know that the long run impact of
the money supply shock must be a proportionate depreciation in
the exchange rate?
Dornbusch's brilliant answer is that the initial depreciation of
the exchange rate must, on impact, be larger than the longrun depreciation. The exchange rate must overshoot.
The volatility of m implies the volatility of e
What are prices doing?
yt  y   (et  p *  pt  q)
pt 1  pt   ( y  y)
Hp: Announcement in t of a permanent increase in the
money supply m a t+3
The potential for arbitrage profits rules out the possibility of any
discrete jump of e; no jumps in the instant in which the policy is
e will jump at the announcement
The depreciation generate an excess demand for goods,
therefore p increases
An increase in p implies a reduction in m/p and an increase in i
i higher than i* implies further expected depreciation ,,,e and p
will continue to increase until t+3 when m increases
At this point i is below i* therefore expected appreciation, the e
must be above its long run level
Evidence for and against the model
To test the model many have used
Frankel's (1979) observation that, under a
reasonably general set of assumptions,
Dornbusch model predicts that high real
interest rates will cause the real
exchange rate to appreciate.
 Looking at data: the model captures
major turning points in monetary policy
quite well, however, it does not seem to
capture all the other big exchange rate
swings that regularly take place.
Dollar/€ Exchange Rate: Where
Substantial $ depreciation since spring 2002 (20%)
Recent movements: expectations
vs fundamentals
Following the call for more flexibility for “more
flexibility in the exchange rate” of major
countries (IMF/WB annual meetings sept 03,
G7 communiqué), the $ experienced a rather
broad weakening while the yen rose to its
highest level in 3 years.
 Following the remarks by Duisenberg that the
flexibility was not so much for the $/€
exchange rate but for the Asian regimes, the
$ recovered
Recent data on US labour market and growth
resulted in a further appreciation of the $
 However there is a general consensus that the
$ should weaken further, Why? Because of the
“unsustainable” current account deficit, which
has reached 5% of GDP
 Bergsten (IIE Washington 2003) “to finance
both the current account deficit and our sizable
capital exports, the US must import about $1
trillion of foreign capital every year, more than
$4 billion every working day. The situation is
clearly unsustainable.” … “the trade-weighted
average exchange rate of the $ needs to fall
by another 10-15 %..the decline should occur
against a broader group of currencies”
A similar view, but a stronger position on the
$/€ exchange rate.
 Lynn (Bloomberg 12 Nov 2003): The
appreciation of the € will not last .. some
figures: from July to Sept the US economy
expanded at a rate of 7.2% and Europe? In
the second quarter, the euro-countries
contracted by 0,1%. Unemployment in
Europe is still at about 9%, Germany,
Europe’s largest economy