How Market Intervention can Prevent Bubbles and Crashes: An Agent Based Modelling Approach

Using a previously validated agent-based model with fundamentalists and chartists, we investigate the usefulness and impact of direct market intervention. The policy maker diagnoses bubbles by forming an expectation of the future returns, then invests in burgeoning bubbles to develop a sufficient inventory of the risky asset in order to be able to sell adequate amounts of the overpriced asset later countercyclically to fight market exuberance. Preventing bubbles and crashes, this market intervention improves all analysed market return metrics, volatility, skewness, kurtosis and VaR, without affecting long-term growth. This increases the Sharpe ratios of noise traders and of fundamentalists by approximately 28% and 45% respectively. The results are robust even for substantially miscalibrated long-term expected returns.