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Hongseok Choi

aitch.choi@gmail.com

  • Sejong University, 03/2026–

- Associate Professor, Department of Economics

  • Korea Institute for International Economic Policy (KIEP), 08/2023–02/2026

- Research Fellow, International Finance Team, 01/2025–02/2026 

- Associate Research Fellow, International Finance Team, 08/2023–12/2024

  • City University of Hong Kong, 05/2016–06/2023

- Assistant Professor (Finance), Department of Economics and Finance

Ph.D. in Economics, University of Pennsylvania, 2012

M.A.   in Economics, University of Pennsylvania, 2011

B.Sc.  in Physics and B.A. in Economics, Summa cum Laude, Seoul National University, 2006

Curriculum Vitae

Working Papers

  • Ambiguous State Dynamics, Learning, and Endogenous Long-Run Risk

Revise and Resubmit at the Journal of Economic Theory

This paper considers learning about unobservable state variables when their dynamics are ambiguous. The drift of the state process is perturbed and set-estimated by inverting a test. The evolution of the set estimate is explicitly characterized up to a system of differential equations extending the conditionally Gaussian filter and is embedded in recursive maxmin expected utility. Despite the fact that the agent is unconfident only about the drift of the state process, learning under ambiguity makes her behave as if she assumed excessive volatility for the state process. This helps explain why the long-run risk model elicits seemingly excessive long-run risk from returns data.

Supplementary Appendix


  • Do People Follow AI Advice? Evidence from a Pension Portfolio Choice Experiment, with Jeongbin Kim, Matthew Kovach, Kyu-Min Lee, Euncheol Shin, and Hector Tzavellas

We study how differences in AI-generated financial recommendations are transmitted into individual portfolio choices. In an experiment with 400 employed adults enrolled in workplace defined contribution pension plans in South Korea, participants allocate a hypothetical pension balance across eleven products and may revise it after receiving one of two fixed AI-generated recommendations. A 2×2 design randomizes recommendation content and whether the recommendation includes a short rationale. Approximately 37% of the experimentally induced difference between the aggressive and conservative recommendations passes through to final portfolios. This causal contrast changes expected portfolio return, volatility, allocations across risk grades, and the number of products held, but produces no detectable difference in computed Sharpe ratios. 81% of participants revise. Among revisers, 95% move toward the assigned recommendation and implement about half of the suggested adjustment. Rationales do not detectably alter pass-through. These results show that users partially and selectively transmit recommendation content into economically meaningful differences in risk exposure while retaining substantial weight on their initial choices.

Publications

  • Learning about Ambiguous Long-Term Prospects, 2026, Journal of Economic Theory

  • On the Timing Premium Puzzle, 2025, Economics Letters

Supplementary Appendix

Work in Progress

  • Can Learning Reduce the Dark Matter in the Long-Run Risk Model?

General Research Fund, Hong Kong Research Grants Council, 01/2022–12/2023

Research Interests

Theoretical Asset Pricing, Portfolio Choice, Decision Making under Ambiguity

Teaching

Sejong University, 2026–

  • Principles of Economics

  • Mathematics for Social Sciences

City University of Hong Kong, 2016–2023

  • Derivatives and Risk Management

  • Fixed Income Securities

  • Stochastic Calculus for Finance

  • Theoretical Asset Pricing (Part 2/4)

  • Financial Management

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