Research activity information

• The Impact of Earmarked Taxes on Supply Curve Shifts: A Laboratory Experiment

  Shigeharu Okajima, Taro Shinoda, Yukihiko Funaki, Hiroko Okajima

  In this study, we examine how ordinary taxes and earmarked taxes influence tax pass-through in a market experiment. We hypothesize that tax pass-through is lower for earmarked taxes than for ordinary taxes and that this difference depends on market conditions, specifically the balance between the trade surpluses for sellers and buyers. Our findings confirm that ordinary taxes result in full tax pass-through, whereas earmarked taxes result in less pass-through. Under earmarked taxes, sellers adjust the level of pass-through based on their trade surplus relative to the buyers’ trade surplus. These results underscore the need to distinguish between tax types. The results of our study provide novel insights into the resource allocation effects of different tax types, offering significant implications for policymakers seeking to regulate goods with externalities through taxation.

  SAGE Publications, Feb. 2026, Public Finance Review

  [Refereed]

  Scientific journal


• Gender diversity and firm performance: A multi‐level analysis of Japanese firms

  Hiroko Okajima, Shigeharu Okajima, Tomoka Ito, Atsushi Morimoto

  Abstract This study analyzes how gender diversity at the board, managerial, and employee levels relates to firm performance in Japan, using panel data from 311 listed companies (2006–2017). We apply instrumental variable estimation to address endogeneity. Across all levels and models, we find no statistically significant association between female representation and performance (measured by Tobin's Q and profit margin). These insignificant results may reflect structural or cultural barriers that limit the impact of diversity. The findings suggest that increasing female representation alone may be insufficient without broader organizational reform and institutional support mechanisms.

  Wiley, Dec. 2025, Asian Economic Journal, 39(4) (4), 498 - 528

  [Refereed]

  Scientific journal


• Firm age and wage determination: evidence from matched employer–employee data in Japan

  Hiroko Okajima, Kazufumi Yugami, Atsushi Morimoto, Shigeharu Okajima, Kenta Nakamura

  Informa UK Limited, Mar. 2020, Applied Economics Letters, 28(2) (2), 133 - 136

  [Refereed]

  Scientific journal


• What Motivates Donation? Empirical Evidence on Social Cooperation

  Shigeharu Okajima, Fukihiko Funaki, Hiroko Okajima

  Nov. 2018, Kokumin Keizai Zatsushi

  [Refereed]


• Impact of environmental regulation and the 2011 earthquake on the Japanese electricity industry

  Shigeharu Okajima, Hiroko Okajima

  Feb. 2016, 49, 223 - 249

  [Refereed]


• Estimation of Japanese price elasticities of residential electricity demand, 1990–2007

  Shigeharu Okajima, Hiroko Okajima

  Elsevier BV, Nov. 2013, Energy Economics, 40, 433 - 440

  [Refereed]

  Scientific journal


• Analysis of energy intensity in Japan

  Shigeharu Okajima, Hiroko Okajima

  Elsevier BV, Oct. 2013, Energy Policy, 61, 574 - 586

  [Refereed]

  Scientific journal

• 行動経済学会


• European Association of Environmental and Resource Economists


• American Economic Association


• 日本経済学会

• -

  Competitive research funding