But such interventions are complicated – not least because they must account for the relationship between the country’s monetary-policy approach and that of other relevant countries. Moreover, if, for example, the United States aims for ¥100 per dollar, while Japan aims for ¥120 per dollar, the result could be not only rising tension between the US and Japan; incompatible exchange-rate targets could also trigger broader market volatility, with spillover effects on other economies.