A large volatility reflects dispersed opinions among market participants. Even when an FX intervention moves the level of the FX rate in its intending direction, this movement is transient unless the intervention mitigates the volatility and dissolves the dispersion among market participants. I adopt pulse and step functions to examine the short-run dynamic effects of four recent Japanese FX interventions on the level and volatility of the yen/dollar rate. The four interventions are large and public, and these are important factors in the effectiveness of the intervention. I find that the two recent interventions are successful in terms of persistent depreciation and mitigating volatility. The two successful interventions are characterized by their size effect. In turn, although the third intervention caused the yen to depreciate, this is short-lived because of increasing volatility.

大幅波动反映出市场参与者之间的意见分散。即使外汇干预使外汇汇率的水平朝其预期的方向移动，这种移动也是短暂的，除非干预措施减轻了波动性并消除了市场参与者之间的分散。我采用脉冲和阶跃函数来研究最近四种日本外汇干预对日元/美元汇率的水平和波动性的短期动态影响。这四种干预措施既大型又公开，是影响干预措施有效性的重要因素。我发现最近的两种干预措施在持续贬值和减轻波动方面均取得了成功。两种成功的干预措施均具有规模效应的特点。反过来，尽管第三次干预导致日元贬值，