Portfolio Optimization under Recursive Utility via Reinforcement Learning
Portfolio Optimization under Recursive Utility via Reinforcement Learning
This paper integrates recursive utility, a risk-sensitive objective from asset-pricing theory, into actor-critic reinforcement learning for portfolio allocation. The recursive utility framework separates risk aversion from intertemporal substitution, which is not captured by standard discounted sum of rewards. The authors approximate the certainty equivalent of future value using K-sample Monte Carlo and derive a Bellman residual-based advantage estimate (AAE) that generalizes to multi-step returns with state-dependent weights. The method is applicable only to critic-based algorithms like PPO and A2C, as it requires a learned value function.
Experiments on 10 chronological train/test splits of South Korean ETF data show that the recursive-utility agent improves upon the naive (discounted) baseline in Sharpe ratio (2.07 vs 1.22), max drawdown (10.38% vs 12.26%), and cumulative return (8.23% vs -6.47%). It also outperforms a Markowitz-based reward objective. However, the equal-weight (1/N) benchmark still achieves higher Sharpe ratios (2.3-2.7), indicating that the RL agents have room for improvement. The results are consistent with a risk-sensitive objective that penalizes downside dispersion, but high variance across splits and sensitivity to hyperparameters suggest caution in interpretation. The paper provides detailed derivations, experiment setup, and ablation studies in the appendices.
Highlights
- 1Integrates recursive utility from asset-pricing theory into actor-critic RL for portfolio optimization, separating risk aversion from intertemporal substitution.
- 2Proposes a Monte Carlo sampling-based certainty equivalent to approximate the non-linear Bellman target under recursive utility.
- 3Introduces an approximate advantage estimate (AAE) that generalizes the Bellman residual to multi-step with state-dependent weights.
- 4Demonstrates improved Sharpe ratio, max drawdown, and cumulative return over naive and Markowitz baselines on South Korean ETF data.
- 5Restricts the formulation to critic-based algorithms (PPO, A2C) due to the need for a learned value function.
Methods
- MRecursive utility Bellman equation with CES aggregator and CRRA risk aggregation.
- MK-sample Monte Carlo estimation of the certainty equivalent of future value.
- MActor-critic algorithms (PPO, A2C) with recursive utility value target and approximate advantage estimation (AAE).
- MCampbell-Viceira approximate rules for actor initialization.
Results
- RRecursive utility PPO achieves higher Sharpe ratio (2.07 vs 1.22) and lower max drawdown (10.38% vs 12.26%) compared to naive baseline.
- RRecursive utility yields higher cumulative return (8.23% vs -6.47%) than naive baseline.
- RRecursive utility outperforms Markowitz objective (Sharpe 1.43) under PPO.
- REqual-weight (1/N) benchmark still outperforms all RL agents (Sharpe 2.3-2.7), indicating room for improvement.
- RHigh variance across splits and sensitivity to hyperparameters (K, training window) observed in ablation study.
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