Downside risk control and optimal investment turnover around financial crises

摘要

This paper investigates tactical investment strategies for investors to survive financial crises. Compared with the buy-and-hold strategy, the buy-and-sell strategy is much more effective in mitigating downside risk before, during, and after a crisis by restricting the left-tail volatility of portfolio returns through CVaR constraints. The paper also studies investors' optimal turnovers around a crisis under the buy-and-hold strategy. Considering investors' heterogeneous behaviours, we find the wealth-weighted average optimal turnover across all investors during a crisis is much higher than that before or after the crisis. This indicates investors who enter the market before a crisis may be better off by leaving their portfolios untouched during the market downturn. In addition, the downside risk control model can detect a market downturn earlier than the mean-variance model therefore it helps to 'spread out' the required asset adjustments over a longer horizon than the crisis period itself.