The best Forex dealers understand supply and demand effects the market and make investments based off predicting future changes in currency exchange rates. The laws of supply and demand are: when supply is plentiful the price of that item should be low and when a product is limited in amount it causes the price to go up high. The National currency rates are directly associated with supply and demand. Also, as central banks adjust their interest rates, the Forex market may experience an incline or decline. Forex dealers work hard at predicting the central banks actions to increase the chance of incline.