Each country in the world has its own currency. As a result of international trade, these currencies are constantly being traded for each other. Changes in the supply of and the demand for these currencies cause changes in the exchange rates between currencies.
Currency Converter: convert currencies with current exchange rates
Historical Exchange Rates: from PACIFIC Exchange Rate Service
Purchasing Power Parity: in the long tun, countries’ exchange rates should move towards rates that would equalize the prices of an identical basket of goods and services. The Economist uses a MacDonald’s Big Mac, which is produces in 120 countries, as its basket. The Big Mac Index is then used to determine if a countriy’s currency is overvalued or undervalued, compared to the dollar.