在实践中,大规模交易者往往面临着价格冲击的内生流动性风险,因此交易者往往将其头寸进行分割、选择最优策略进行交易。我们对价格冲击模型作了一般性拓展,在交易对价格的影响为更接近于市场一般情况的随机、非线性价格冲击,建立了随机非线性价格冲击模型;以投资者的头寸变化作为交易策略的反映,结果表明在随机条件下考虑非线性价格冲击(二次价格冲击函数)时,投资者的变现速度明显地受到限制,在变现期的绝大部分时间内以恒定速度变现,同时对最优策略进行了参数的敏感性分析:价格波动系数一、风险厌恶系数α越大,则前期变现速度越大、资产头寸减少越快;价格冲击系数γ、β及瞬时价格冲击波动率θ的增加,变现头寸的减少越接近于直线的形式。另外我们强调在决定最优变现时间时既要考虑内生最优变现时间而且也要考虑外在条件的要求,最终最优变现时间应是内外因素综合考虑的结果。
In practice, the trader with a large block of shares usually faces endogenous liquidity risk of price impact. So the shares are usually broken up and the trader chooses the optimal strategy to trade. In this paper, the model of price impact is expanded. Supposing price impact with stochastic and nonlinear, we established the model of the stochastic and nonlinear price impact. The results show that the trader liquidation speed is obviously confined and the speed is constant under stochastic and quadratic price impact function. The parameters sensitivity of optimal strategy is also analyzed in the paper: in early days, the greater α and a are, the greater liquidation speed is. The liquidation position reduction is more close to linear with γ, β and θ increasing. We also highlight that the optimal liquidation time should be investigated under internal and external conditions.