how does a currency lose or gain value
Currency appreciation and depreciation In a floating exchange rate system, a currency's value goes up (or down) if the demand for it goes up more (or less) than the supply does. In the short run this can happen unpredictably for a variety of reasons, having to do with trade flows, speculation, or other factors in the international capital market. For example, a surge in purchases of foreign goods by home country residents will cause a surge in demand for foreign currency with which to pay for those goods, causing a depreciation of the home currency.