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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

  • Korean Air Force, 09/2012–11/2015

- 1st Lieutenant/Assistant Professor (Mandatory Military Service)

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 extends the Kalman–Bucy–Liptser–Shiryaev filter (Kalman and Bucy, 1961; Liptser and Shiryaev, 1974) to a case of ambiguous state dynamics. The extension shows that ambiguity about the drift of the state process translates, through learning, into additional volatility for the process. This helps rationalize the seemingly excessive long-run risk (LRR) implied by stock returns. The generalized filter is embedded in recursive maxmin expected utility and applied to asset pricing to demonstrate that the endogenous LRR indeed improves the performance of the LRR model: With learning under ambiguity, the predictability of consumption growth decreases while that of stock returns increases; and the estimated elasticity of intertemporal substitution decreases.

Supplementary Appendix


  • How Much Do Investors Follow AI Advice? Recommendation Pass-Through in a Pension Portfolio Experiment, with Jeongbin Kim, Matthew Kovach, Kyu-Min Lee, Euncheol Shin, and Hector Tzavellas

We identify how recommendation content passes through to pension portfolios. In an experiment, 400 South Korean defined contribution plan participants choose portfolios before and after random assignment to two AI-generated recommendations. Along the axis connecting them, 36.8 percent of the induced gap passes through to portfolios. Content shifts return, volatility, risk allocations, and breadth, with no detectable effects on Sharpe ratios or concentration. Eighty-one percent revise. Among revisers, 95 percent move toward the recommendation but implement half of the suggested adjustment. Rationales have no statistically reliable effect on pass-through. Content thus shifts risk exposure despite incomplete implementation.

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

Finance (Theoretical Asset Pricing, Portfolio Choice), Microeconomics (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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