Optimal Consumption and Investment with Income Adjustment and Borrowing Constraints

In this paper, we address the utility maximization problem of an infinitely lived agent who has the option to increase their income. The agent can increase their income at any time, but doing so incurs a wealth cost proportional to the amount of the increase. To prevent the agent from infinitely inc...

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Main Authors: Geonwoo Kim, Junkee Jeon
Format: Article
Language:English
Published: MDPI AG 2024-11-01
Series:Mathematics
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Online Access:https://www.mdpi.com/2227-7390/12/22/3536
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author Geonwoo Kim
Junkee Jeon
author_facet Geonwoo Kim
Junkee Jeon
author_sort Geonwoo Kim
collection DOAJ
description In this paper, we address the utility maximization problem of an infinitely lived agent who has the option to increase their income. The agent can increase their income at any time, but doing so incurs a wealth cost proportional to the amount of the increase. To prevent the agent from infinitely increasing their income and borrowing against future income, we additionally consider a non-negative wealth constraint that prohibits borrowing based on future income. This utility maximization problem is a mixture of stochastic control, where the agent chooses consumption and investment, and singular control, where the agent chooses a non-decreasing income process. To solve this non-trivial and challenging problem, we derive the Hamilton–Jacobi–Bellman (HJB) equation with a gradient constraint using the dynamic programming principle (DPP). Then, using the guess-and-verify method and a linearization technique, we obtain a closed-form solution to the HJB equation and, based on this, find the optimal strategy.
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spelling doaj-art-3bf8e87f006645ddb495c65064d7521d2025-08-20T02:05:04ZengMDPI AGMathematics2227-73902024-11-011222353610.3390/math12223536Optimal Consumption and Investment with Income Adjustment and Borrowing ConstraintsGeonwoo Kim0Junkee Jeon1School of Natural Sciences, Seoul National University of Science and Technology, Seoul 01811, Republic of KoreaDepartment of Applied Mathematics, Kyung Hee University, Yongin 17104, Republic of KoreaIn this paper, we address the utility maximization problem of an infinitely lived agent who has the option to increase their income. The agent can increase their income at any time, but doing so incurs a wealth cost proportional to the amount of the increase. To prevent the agent from infinitely increasing their income and borrowing against future income, we additionally consider a non-negative wealth constraint that prohibits borrowing based on future income. This utility maximization problem is a mixture of stochastic control, where the agent chooses consumption and investment, and singular control, where the agent chooses a non-decreasing income process. To solve this non-trivial and challenging problem, we derive the Hamilton–Jacobi–Bellman (HJB) equation with a gradient constraint using the dynamic programming principle (DPP). Then, using the guess-and-verify method and a linearization technique, we obtain a closed-form solution to the HJB equation and, based on this, find the optimal strategy.https://www.mdpi.com/2227-7390/12/22/3536income adjustmentconsumption and investmentHJB equationsingular controlfree boundary problemlinearization
spellingShingle Geonwoo Kim
Junkee Jeon
Optimal Consumption and Investment with Income Adjustment and Borrowing Constraints
Mathematics
income adjustment
consumption and investment
HJB equation
singular control
free boundary problem
linearization
title Optimal Consumption and Investment with Income Adjustment and Borrowing Constraints
title_full Optimal Consumption and Investment with Income Adjustment and Borrowing Constraints
title_fullStr Optimal Consumption and Investment with Income Adjustment and Borrowing Constraints
title_full_unstemmed Optimal Consumption and Investment with Income Adjustment and Borrowing Constraints
title_short Optimal Consumption and Investment with Income Adjustment and Borrowing Constraints
title_sort optimal consumption and investment with income adjustment and borrowing constraints
topic income adjustment
consumption and investment
HJB equation
singular control
free boundary problem
linearization
url https://www.mdpi.com/2227-7390/12/22/3536
work_keys_str_mv AT geonwookim optimalconsumptionandinvestmentwithincomeadjustmentandborrowingconstraints
AT junkeejeon optimalconsumptionandinvestmentwithincomeadjustmentandborrowingconstraints