The answer to this question is student specific. Government intervention can help smooth out temporary fluctuations in exchange rates. However, this is often problematic since at the time a currency appreciation occurs, the government can never be sure whether a disturbance is transitory and soon likely to reverse itself or more persistent and fundamental in nature. If unstable exchange rate expectations lead to capital flows that cause exchange rate movements and undesired changes in domestic output, central bank intervention seems justified. But central banks also often intervene to try to reduce inflation by preventing import prices from rising. The cost of reducing inflation in this way is a steady loss in competitiveness, which may even result in a foreign exchange crisis. Ultimately, inflation has to be stopped by restrictive monetary policy. Central banks may also intervene to affect trade flows and to bring about desired changes in domestic output. In the long run, however, governments are better off not opposing strong market forces by intervening in the foreign exchange market. If a government really wants to bring about change, it should employ domestic policies. It may supplement its policy by intervening in the foreign exchange market as well to emphasize its intent.
Government intervention is more effective if it is backed up by credible policies. There is evidence that non-sterilized intervention affects exchange rates more successfully, since there is a change in money supply equal to the amount of the intervention. But if the intervention is sterilized, domestic money supply will remain unchanged and even a massive intervention may not affect the exchange rate to the desired degree.
參考答案:这个问题的答案是特别针对学生的。政府的干预可以帮助熨平汇率的暂时波动。但是，也存在这样一个问题，政府不能确定这个波动是否是暂时、很快逆转的或者是更持久的。不稳定的汇率预期导致资金流动，从而造成汇率波动和国内产出的不利变化，此时央行的干预就看起来是合理的。但是央行的干预常常是企图通过抑制进口价格的上升来阻止通货膨胀。这样做的成本就是本国产品竞争力的削弱进而导致外汇危机。最终，政府只能通过紧缩的货币政策阻止通货膨胀。央行同样会通过干预贸易流动来得到合适的国内产出变化。但是在长期，政府最好是通过干预外汇市场而不是对抗强大的市场力量。如果政府真的想要改变的话，就会采取国内的政策。干预外汇市场只是强调这一目的的补充。
政府干预在有可靠政策支持的情况下才会更有效。证据证明未充销干预会更成功的影响汇率，因为货币供给的变动和干预的总量是平衡的。但如果干预是充销性的，国内的货币供给将保持不变，即使很强的干预也不会使汇率到变动到一个期望的水平。
