Asymmetric Nonlinear Return Extrapolation and Optimal Portfolio Choice under Stochastic Volatility
随机波动率下的非对称非线性回报外推与最优投资组合选择
Dong Yan, Wenrui Ye, Zhiyue Zong, Wenting Chen
AI总结 将回报外推扩展至非对称非线性信念更新,求解Heston随机波动率下CRRA投资者的最优投资组合,发现饱和效应作为内生修正机制降低福利损失。
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我们将Atmaz (2022)的回报外推框架扩展,纳入线性基准中缺失的两个行为现实特征:信念更新的饱和性以及收益与损失之间的非对称性。我们引入一个平滑、非线性、非对称的外推函数,并将Heston (1993)随机波动率下CRRA投资者的最优投资组合刻画为情绪扭曲的投机需求、方差对冲需求和情绪对冲需求之和。由此产生的半线性Hamilton-Jacobi-Bellman方程通过两种独立数值方法求解:带时间步策略迭代的有限差分ADI格式和深度学习驱动的迭代格式。该模型产生了四个投资者层面的行为异常:对收益和损失的非对称反应、极端情况下的反应减弱、过度交易量以及随外推强度增加的福利损失,每个异常都与已记录的经验模式相对应。其核心发现是饱和效应作为一种内生修正机制:在原点处相同局部斜率下,非对称非线性外推者比线性外推者承受更小的福利损失。
We extend the return extrapolation framework of Atmaz (2022) to incorporate two behaviorally realistic features absent from the linear benchmark: saturation in belief updating and asymmetry between gains and losses. We introduce a smooth, nonlinear, asymmetric extrapolation function and characterize the optimal portfolio of a CRRA investor under Heston (1993) stochastic volatility as the sum of a sentiment-distorted myopic demand, a variance hedging demand, and a sentiment hedging demand. The resulting semilinear Hamilton-Jacobi-Bellman equation is solved by two independent numerical methods, a finite-difference ADI scheme with time-step policy iteration and a deep learning-driven iterative scheme. The model generates four investor-level behavioral anomalies: asymmetric responses to gains and losses, attenuated reactions at extremes, excess trading volume, and welfare loss rising with the strength of extrapolation, each of which maps onto documented empirical patterns. Its central finding is that saturation acts as an endogenous correction mechanism: at the same local slope at the origin, the asymmetric nonlinear extrapolator carries a smaller welfare loss than a linear one.