On Relation Between Margin and Conditional Volatility in Japanese Stock Market

This paper investigates the asymmetric volatility between conditional volatility and initial margin using daily market return of TOPIX and Nikkei225 over 1970 to 1990. In prior studies, generally, it has been known that margin is regard as a main discipline to control volatility with respect to a policy tool. Our empirical test provides the following results. First, this paper shows that there is significantly positive relation between return of stock market and margin, implying that as margin increases, also return increases. Thus we conclude that the trade-off of risk and return is found. Second, our result suggests that in normal state, margin affects to conditional volatility negatively and significantly, indicating that margin policy could control the conditional volatility. Third, this paper finds that in recession state, there is little bit evidence of discipline action in controlling volatility. Fourth, our paper also finds that in boom state, there is adversely evidence of margin on conditional volatility. As a result, government has motivation to decrease the volatility in bull market state, whereas it also has motivation to increase the volatility in bear market state. Our paper finds the evidence that the motive for changing the margin is fitted to normal and boom state. Therefore, our result suggests that government has to adjust the change of margin policy adequately to fit the market conditions.