There are a number of political and economic issues that normally affect the curreny prices. But that said and done, the interest rates, inflation, political stability and international trade are among the common conditions that determine the currency prices. In some instances, some governments take part in foreign exchange markets in order to manipulate the value of their currencies. They can decide to flood the market in question with their particular domestic currency with the hope of lowering the price. This is commonly referred to as central bank intervention.