Rational bubbles and non-risk neutral investors in Japan

This paper presents a sufficient condition for not observing rational bubbles in real stock prices when investors are not risk neutral and both the real interest rate and the risk premium are time varying. If the risk premium and the real interest rate are stationary, the stationarity of the first differences of real stock prices is a sufficient condition for the absence of rational bubbles. Testing this condition with data on Japanese stock prices, we find that the hypothesis that rational bubbles existed is rejected.