This paper explores the shape of the Japanese money demand function in relation to the historical path of the Bank of Japan's policy rate by employing Saikkonen and Choi's [Econometric Theory 20, 301–340 (2004)] cointegrating smooth transition model. The nonlinear model provides a unified econometric framework, not only for pursuing the time profile of interest elasticity, but also to test the linearity of the Japanese money demand function. The test results for the linearity of the Japanese money demand function provide evidence of nonlinearity with a semilog model and linearity with a double-log model. Using a nonlinear semilog model, the analysis also finds that Japanese money demand comprises three regimes and that the interest semielasticity began to increase in the early 1990s when the Bank of Japan set the policy rate below 3%.
