Submitted:
29 May 2026
Posted:
01 June 2026
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Abstract
Keywords:
1. Introduction
- 1.
- We formulate and solve an optimal consumption and investment problem with bounded memory under Epstein-Zin recursive utility. The latter framework naturally generalises the classical CRRA utility case as a particular specification of the preference parameters; see Remark 1.
- 2.
- We introduce a multi-asset incomplete-market model in which each risky asset is influenced by two distinct information-learning mechanisms: an integrated delayed wealth variable reflecting exponentially weighted past performance and a pointwise delayed wealth state representing lagged wealth information. Compared with existing bounded-memory models, our formulation focuses on exponentially weighted gains and losses relative to a benchmark wealth level rather than on absolute historical wealth or on pure average gains and losses.
- 3.
- Using an FBSDE approach together with an explicit ansatz for the value function, we derive closed-form expressions for the optimal consumption and portfolio strategies, as well as the associated value function; see Theorem 1. These explicit formulas make it possible to perform a detailed sensitivity analysis with respect to the memory horizon, learning parameters, risk aversion coefficient, and elasticity of intertemporal substitution.
- 4.
- We provide an economic interpretation of the resulting optimal strategies and show how behavioural learning effects can generate different investment patterns across risky assets. In particular, the analysis highlights the interaction between delayed information, recursive preferences, and dynamic portfolio allocation.
2. Model and Problem Formulation
2.1. Probability Setting and Wealth Process of the Investors
- Let be the set of non-negative progressively measurable processes on .
- Let denote the space of càdlàg adapted -valued processes such that .
- Let denote the space of predictable -valued processes such that .
3. Main Results
3.1. The Epstein-Zin Utility Maximisation with Bounded Memory
- (i)
- Equations (7)-(8) provide a reformulation of the standard Epstein-Zin utility, denoted here by . The standard utility has a terminal value given by , and its generator is defined in the difference form: (see, e.g., Xing (2017, Eq.(2.1)-(2.2))). Note that, corresponds to the standard Epstein-Zin utility if and only if coincides with the utility process defined by Equations (7)-(8). In particular, this implies .
- (ii)
- With the function f parameterised as above, one readily recognises the CRRA utility as a special case corresponding to the parameter configuration (in that case ).
3.2. The Ansatz
3.3. Solution to the Stochastic Optimisation Problem
4. Sensitivity Analysis
5. Conclusions
Author Contributions
Funding
Conflicts of Interest
Appendix A. Proof of Proposition 1
Appendix B. Proof of Theorem 1
- Using Seiferling and Seifried (2016, Thm. 3.1) (see also Kraft et al. (2017, on p.191)), if then for all . This yields the class (D) property of . Recall that . For , we haveBesides,where the last equality holds due to the process , being a martingale. Hence,
- This follows directly from , with ; see right below Equation (6).
- Plugging the expressions of and , the dynamics of the wealth becomeswith the processes and given by Equations (1) and (3), respectively, and Y and Z given by Equation (24). Hence, the wealth process is solution of a stochastic differential equation of type similar to the one studied by Mohammed (1998). Using Mohammed (1998, Thm. I.1), we deduce that the wealth equation admits a unique strong solution.
-
Hence, the process , is of class (D) on as a product of a bounded function and a martingale.
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| Parameter | Symbol | Values |
| Interest rate | r | |
| Risk premium of risky asset 1 | ||
| Risk premium of risky asset 2 | ||
| Volatility of risky asset 1 | ||
| Volatility of risky asset 2 | ||
| Correlation coefficient between risky assets | ||
| Terminal time | T | 10 |
| Initial wealth | 100 | |
| Risk aversion coefficient | 10 | |
| Elasticity of Intertemporal Substitution (EIS) | ||
| Time preference rate | ||
| Average parameter | ||
| Information learning horizon | h | |
| Information learning parameter for the pointwise delayed wealth | ||
| Information learning parameter for the integrated delayed wealth | ||
| Weight parameter for the pointwise delayed wealth |
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