In contrast with the BOP theory of foreign exchange, in which the rate of exchange is determined by the flow of funds in the foreign exchange market, the monetary approach postulates that the rates of exchange are determined through the balancing of the total demand and supply of the national currency in each country. Basically, what we’re talking about is the risk of changes in the relative values of different currencies, which in turn can affect your business’s revenue, costs, cash flow, and profits. You might see this referred to as currency risk, exchange rate risk, or foreign exchange risk—they’re all essentially the same thing. Determination of Exchange Rates: Theory # 1. Purchasing Power Parity Theory: Assuming non-existence of tariffs and other trade barriers and zero cost of transport, the law of one price, the simplest concept of purchasing power parity (PPP), states that identical goods should cost the same in all nations.