Purchasing Power Parity: It states that the price of a good in one country should equal the price of the same good in another country, exchanged at the current rate — the law of one price. There are two versions of the purchasing power parity theory: the absolute version and the relative version. Under the absolute version, the exchange rate simply equals the ratio of the two countries’ general price levels, which is the weighted average of all goods produced in a country. However, this version works only if it is possible to find two countries, which produce or consume the same goods.
Moreover, the absolute version assumes that transportation costs and trade barriers are insignificant. In reality, transportation costs are significant and dissimilar around the world. Trade barriers are still alive and well, sometimes obvious and sometimes hidden, and they influence costs and goods distribution.
Finally, this version disregards the importance of brand names. For example, cars are chosen not only based on the best price for the same type of car, but also on the basis of the name (“You are what you drive”).
Under the PPP relative version, the percentage change in the exchange rate from a given base period must equal the difference between the percentage change in the domestic price level and the percentage change in the foreign price level. The relative version of the PPP is also not free of problems: it is difficult or arbitrary to define the base period, trade restrictions remain a real and thorny issue, just as with the absolute version, different price index weighting and the inclusion of different products in the indexes make the comparison difficult and in the long term, countries’ internal price ratios may change, causing the exchange rate to move away from the relative PPP.
In conclusion, the spot exchange rate moves independently of relative domestic and foreign prices. In the short run, the exchange rate is influenced by financial and not by commodity market conditions.
Theory of elasticities: The theory of elasticities holds that the exchange rate is simply the price of foreign exchange that maintains the balance of payments in equilibrium. In other words, the degree to which the exchange rate responds to a change in the trade balance depends entirely on the elasticity of demand to a change in price. For instance, if the imports of country A are strong, then the trade balance is weak. Consequently, the exchange rate rises, leading to the growth of country A’s exports, and triggers in turn a rise in its domestic income, along with a decrease in its foreign income. Whereas a rise in the domestic income (in country A) will trigger an increase in the domestic consumption of both domestic and foreign goods and, therefore, more demand for foreign currencies, a decrease in the foreign income (in country B) will trigger a decrease in the domestic consumption of both country B’s domestic and foreign goods, and therefore less demand for its own currency.
The elasticities approach is not problem-free because in the short term the exchange rate is more inelastic than it is in the long term and additional exchange rate variables arise continuously, changing the rules of the game.
Modern monetary theories on short-term exchange rate volatility. The modern monetary theories on short-term exchange rate volatility take into consideration the short-term capital markets’ role and the long-term impact of the commodity markets on foreign exchange. These theories hold that the divergence between the exchange rate and the purchasing power parity is due to the supply and demand for financial assets and the international capability.
One of the modern monetary theories states that exchange rate volatility is triggered by a one time domestic money supply increase, because this is assumed to raise expectations of higher future monetary growth.
The purchasing power parity theory is extended to include the capital markets. If, in both countries whose currencies are exchanged, the demand for money is determined by the level of domestic income and domestic interest rates, then a higher income increases demand for transactions balances while a higher interest rate increases the opportunity cost of holding money, reducing the demand for money.
Under a second approach, the exchange rate adjusts instantaneously to maintain continuous interest rate parity, but only in the long run to maintain PPP. Volatility occurs because the commodity markets adjust more slowly than the financial markets. This version is known as the dynamic monetary approach.
Synthesis of traditional and modern monetary views. In order to better suit the previous theories to the realities of the market, some of the more stringent conditions were adjusted into a synthesis of the traditional and modern monetary theories.
A short-term capital outflow induced by a monetary shock creates a payments imbalance that requires an exchange rate change to maintain balance of payments equilibrium. Speculative forces, commodity markets disturbances, and the existences of short-term capital mobility trigger the exchange rate volatility. The degree of change in the exchange rate is a function of consumers’ elasticity of demand. Because the financial markets adjust faster than the commodities markets, the exchange rate tends to be affected in the short term by capital market changes, and in the long term by commodities changes.
