A central bank which chooses to implement a fixed exchange rate policy may face a situation where supply and demand would tend to push the value of the currency lower or higher (an increase in demand for the currency would tend to push its value higher, and a decrease lower) and thus the central bank would have to use reserves to maintain its fixed exchange rate. Under perfect capital mobility, the change in reserves is a temporary measure, since the fixed exchange rate attaches the domestic monetary policy to that of the country of the base currency. Hence, in the long term, the monetary policy has to be adjusted in order to be compatible with that of the country of the base currency. Without that, the country will experience outflows or inflows of capital.