Think
for instance of the car selling business in a small village. At first
there will be just a few car vendors. As the village grows, more and
more people will need cars to satisfy their needs, pushing up the demand
for cars. At this point the demand for cars is greater than the
quantity supplied, pushing prices up. As people realize selling cars is
such a great business opportunity, more people will be attracted the car
business and will start selling cars. As this happens, more and more
cars will be available, pushing up the supply of cars. At some point,
the supply will be greater than the demand of cars. If car vendors don't
lower their prices, they won’t be able to sell their cars, so they are
forced to lower them.
The
same goes for currencies, when a currency increases its value, the
demand is greater than its supply. When a currency decreases its value,
its supply is greater than its demand.
What factors influence the supply and demand of one currency?
The two main factors that influence the movements in one exchange rate are:
1. The capital flows
2. The trade flows
These
two components constitute what economics call balance of payments. The
main purpose of the balance of payments is to quantify the demand and
supply for a currency of one country, over a period of time.
Balance of Payments = Capital Flows + Trade Flows
A
negative balance of payments indicates that the capital leaving the
country is greater than the capital entering the country (not much
demand)
A
positive balance of payments means that the capital entering the
economy is greater than the capital leaving the economy (increasing
demand of the domestic currency)
Theoretically, a balance of payments equal to zero indicates the right value of one currency.
Capital Flows
Capital flows is the net quantity of currency traded (bought or sold) through capital investments.
The capital flow can be divided into: physical flows and portfolio investments.
Physical Flows - They happen when foreign entities sell their local currency and buy foreign currency to make foreign direct investments (for joint
ventures, acquisitions, etc.) When the volume of this kind of
investment increases, it reflects the good shape and health of the
economy where it is invested.
Portfolio investments
- These are investments made on global markets, variable and fixed
income market investments (Forex, stocks, T-bills, etc.) An example of
portfolio investments is when a hedge fund in Japan invests in the US
equity markets.
Trade Flows
Trade
flows measure the net exports and imports of a given country. These two
components (exports and imports) constitute what economists call the
current account.
Countries
that have a positive current account (exports greater than imports) are
more likely to depreciate their currency; this way the consumer abroad
will perceive the foreign currency to be cheaper (and can purchase more goods and services). A good example is Japan.
On
the other hand, countries that have a negative current account (imports
greater than exports) are more likely to appreciate their currency
since they need to sell the local currency and buy foreign currency in
order to purchase goods and services. United States is an example of a
net importer country.
Purchasing Power Parity (PPP)
This
theory states that exchange rates are determined by the relative prices
of a similar basket of goods in different countries. In other words,
the ratio of prices of a basket with similar goods of two countries
should be similar to the exchange rate.
If
a Personal Computer in Australia costs AU$1,500, and the same PC in
United States costs US$1,200. According to the PPP, the exchange rate
AUD/USD would be 1.2500 (1,500/1,200).
If
the exchange rate was at 1.3000 (or above 1.2500) it states that in the
long run it will decrease its value until 1.2500 is reached. On the
other hand, if the exchange rate was at 1.0500 (or below 1.2500) the
exchange rate in the long run will increase its value until 1.2500 is
reached.
This example is just illustrative, in the real world it is not just one good, but a basket of goods.
The
major weakness of this theory is that it assumes that there are no
costs related to the trade of goods (tariffs, taxes, etc). Another
weakness is that it does not consider other factors that might influence
the exchange rate (i.e. interest rates etc)
Modern monetary theories include the capital markets to the PPP theory arguing that capital markets have less costs of trading.
Interest Rate Theory
This
theory states that interest rates differentials neutralize the increase
or decrease of any currency against another currency. Therefore there
are no arbitrage opportunities.
For
instance if the interest rate of Australia is 6.25% and the interest
rate of United States is 3.5%, then the AUD should depreciate against
the USD, so that there are no arbitrage opportunities.
There
are also other theories that try to explain the value of a currency
pair. But as with every theory, they are based on assumptions that may
or may not be present in the real world.