The econometrics modeling, through a cointegration analysis, suggests that the reaction
function of the BOJ is counter cyclical in relation to exchange rate deviations fromits parity
value. This means that the nominal interest rate decreases each time that the exchange rate
overvalues in relation to its parity value and it is tightened otherwise. The role of the inflation
rate as a target variable is questionable, given that its coefficient in the estimated reaction
function is significantly less than one and it is not weakly exogenous in the model.