Research areas

- Probability - Statistics
- Actuarial Science - Quantitative Risk Management

See Research for more specific topics.

Research Support

- Grant-in-Aid for Early-Career Scientists (2021~2024), Japan Society for the Promotion of Science (JSPS, KAKENHI), Grant number: JP21K13275, Principal Investigator.

- Grant-in-Aid for Scientific Research (B) (2024~2027), Japan Society for the Promotion of Science (JSPS, KAKENHI), Grant number: JP24K00273, Co-investigator.

Affiliated member

- Visiting Assistant Professor, Faculty of Science and Technology, Keio University (2020.12.01 - present)

- Visiting Research Fellow, Risk Analysis Research Center, The Institute of Statistical Mathematics (2022.04.01 - 2024.03.31)

- Visiting Assistant Professor, Risk Analysis Research Center, The Institute of Statistical Mathematics (2024.04.01 - present)

Contact

Graduate School of Economics
Hitotsubashi University
2-1, Naka, Kunitachi, Tokyo 186-8601, Japan

Office: Faculty Building 2, Room 213
Tel: +8142-580-8856
Email: takaaki (dot) koike (at) r.hit-u.ac.jp

Pre-publication Manuscripts

Publications

• Koike, T., Chen, C.W.S. and Lin, E.M.H. (2024). Forecasting and Backtesting Gradient Allocations of Expected Shortfall. Insurance: Mathematics and Economics, 124, 103130. Available at URL.

• Koike, T., Kato, S. and Yoshiba, T. (2025). Measuring and testing tail equivalence. Journal of Multivariate Analysis, 209, 105460. Available at URL.

• Koike, T., Lin, L., and Wang, R. (2024). Invariant correlation under marginal transforms. Journal of Multivariate Analysis, 204, 105361.

• Chen, C.W.S., Koike, T. and Shau, W.H. (2024) Tail risk forecasting with semi-parametric regression models by incorporating overnight information. Journal of Forecasting, 43(5), 1492–1512.

• Koike, T., Lin, L., and Wang, R. (2024). Joint mixability and notions of negative dependence. Accepted by Mathematics of Operations Research.

• Koike, T., and Hofert, M. (2024). Comparison of correlation-based measures of concordance in terms of asymptotic variance. Journal of Multivariate Analysis, 201, 105265. 

• Yoshiba, T., Koike, T. and Kato, S. (2023). On a Measure of Tail Asymmetry for the Bivariate Skew-Normal Copula. Symmetry, 15(7), 1410. Available at URL.

• Koike, T., Kato, S., and Hofert, M. (2023). Measuring non-exchangeable tail dependence using tail copulas. ASTIN Bulletin: The Journal of the IAA. 53(2), 466--487.

• Koike, T., and Hofert, M. (2023). Matrix compatibility and correlation mixture representation of generalized Gini's gamma. Canadian Journal of Statistics. 51(4),1111-1125. 

• Koike, T., Saporito, Y., and Targino, R. (2022). Avoiding zero probability events when computing Value at Risk contributions. Insurance: Mathematics and Economics, 106, 173-192. URL

• Koike, T., and Hofert, M. (2021). Modality for scenario analysis and maximum likelihood allocation. Insurance: Mathematics and Economics, 97, 24-43. URL

• Koike, T., and Hofert, M. (2020). Markov Chain Monte Carlo methods for estimating systemic risk Allocations. Risks, 8(1), 6; https://doi.org/10.3390/risks8010006. URL

• Hofert, M., and Koike, T. (2019). Compatibility and attainability of matrices of correlation-based measures of concordance. ASTIN Bulletin: The Journal of the IAA,  49(3): 885-918.
 URL

• Koike, T., and Minami, M. (2019). Estimation of risk contributions with MCMC. Quantitative Finance, 19(9), 1579-1597. URL

• Koike, T., Minami, M. and Shiraishi, H. (2016). Calculation of value-at-risk bounds using rearrangement algorithm. (in Japanese), Journal of the Japan Statistical Society, 45(2), 353-375. URL

Other Publications and Manuscripts

• Koike, T. (2024). Measuring tail asymmetry of skew normal copula. The Institute of Statistical Mathematics Cooperative Research Report 478, Extreme Value Theory and Applications (22). URL

• Koike, T. (2022). Discussion of tail dependence measures using tail copulas. The Institute of Statistical Mathematics Cooperative Research Report 454, Extreme Value Theory and Applications (19). URL

• Koike, T. (2020). Risk Analysis: Measures of concordance, their compatibility and capital allocation (Doctoral thesis). URL