While the par of exchange of a given monetary unit remains practically stationary, the market price or rate of exchange fluctuates daily. As in the case of any commodity, the market price or rate of exchange of any country varies directly with the demand, and inversely with the supply of bills drawn in terms of the particular currency. This demand and supply is influenced by the following factors: (1) movement of goods and bullion, (2) investment of capital, (3) payment, of services.