Between 2003 and the end of 2004, the AUD/USD currency pair offered a positive yield spread of 2.5%. Although this may seem very small, the return would become 25% with the use of 10:1 leverage. During that same time, the Australian dollar also rallied from 56 cents to close at 80 cents against the U.S. dollar, which represented a 42% appreciation in the currency pair. This means that if you were in this trade – and many hedge funds at the time were – you would have not only earned the positive yield, but you would have also seen tremendous capital gains in your underlying investment.
In every foreign exchange transaction, you are simultaneously buying one currency and selling another. In effect, you are using the proceeds from the currency you sold to purchase the currency you are buying. Furthermore, every currency in the world comes attached with an interest rate set by the central bank of that currency's country. You are obligated to pay the interest on the currency that you have sold, but you also have the privilege of earning interest on the currency that you have bought. For example, let’s look at the New Zealand dollar/Japanese yen pair (NZD/JPY). Let’s assume that New Zealand has an interest rate of 8% and that Japan has an interest rate of 0.5% In the currency market, interest rates are calculated in basis points. A basis point is simply 1/100th of 1%. So, New Zealand rates are 800 basis points and Japanese rates are 50 basis points. If you decide to go long NZD/JPY you will earn 8% in annualized interest, but have to pay 0.5% for a net return of 7.5%, or 750 basis points.
Just like stocks, you can trade currency based on what you think its value is (or where it's headed). But the big difference with forex is that you can trade up or down just as easily. If you think a currency will increase in value, you can buy it. If you think it will decrease, you can sell it. With a market this large, finding a buyer when you're selling and a seller when you're buying is much easier than in other markets. Maybe you hear on the news that China is devaluing its currency to draw more foreign business into its country. If you think that trend will continue, you could make a forex trade by selling the Chinese currency against another currency, say, the US dollar. The more the Chinese currency devalues against the US dollar, the higher your profits. If the Chinese currency increases in value while you have your sell position open, then your losses increase and you want to get out of the trade.
Currencies are traded on the Foreign Exchange market, also known as Forex. This is a decentralized market that spans the globe and is considered the largest by trading volume and the most liquid worldwide. Exchange rates fluctuate continuously due to the ever changing market forces of supply and demand. Forex traders buy a currency pair if they think the exchange rate will rise and sell it if they think the opposite will happen. The Forex market remains open around the world for 24 hours a day with the exception of weekends.