Doctoral Student

Aaron Yoon

Aaron S. Yoon is a doctoral candidate in the Accounting.

His research interests are in the capital market (institutional investors, portfolio management, security analysts, sustainability), with a focus on the forces and mechanisms that shape accounting information.

He holds an MA in Economics and BA in Economics and Mathematical Methods in the Social Sciences from Northwestern University. Prior to Harvard, Yoon worked as an equity trader and quant research analyst at Credit Suisse. He also controlled air traffic in the 8th US Army.

Journal Articles

  1. Corporate Sustainability: First Evidence on Materiality

    Mozaffar Khan, George Serafeim and Aaron Yoon

    Using newly available materiality classifications of sustainability topics, we develop a novel dataset by hand-mapping sustainability investments classified as material for each industry into firm-specific sustainability ratings. This allows us to present new evidence on the value implications of sustainability investments. Using both calendar-time portfolio stock return regressions and firm-level panel regressions we find that firms with good ratings on material sustainability issues significantly outperform firms with poor ratings on these issues. In contrast, firms with good ratings on immaterial sustainability issues do not significantly outperform firms with poor ratings on the same issues. These results are confirmed when we analyze future changes in accounting performance. The results have implications for asset managers who have committed to the integration of sustainability factors in their capital allocation decisions.

    Keywords: sustainability; Investments; corporate social responsibility; accounting; corporate reporting; regulation; Corporate Social Responsibility and Impact; Integrated Corporate Reporting; Investment; Corporate Governance;


    Khan, Mozaffar, George Serafeim, and Aaron Yoon. "Corporate Sustainability: First Evidence on Materiality."Accounting Review (forthcoming). View Details

Working Papers

  1. Shareholder Activism on Sustainability Issues

    Jody Grewal, George Serafeim and Aaron Yoon

    Shareholder activism on sustainability issues has become increasingly prevalent over the years, with the number of proposals filed doubling from 1999 to 2013. We use recent innovations in accounting standard setting to classify 2,665 shareholder proposals that address environmental, social, and governance (ESG) issues as financially material or immaterial, and we analyze how proposals on material versus immaterial issues affect firms’ subsequent ESG performance and market valuation. We find that 58% of the shareholder proposals in our sample are filed on immaterial issues. We document that filing shareholder proposals is effective at improving the performance of the company on the focal ESG issue, even though such proposals nearly never received majority support. Improvements occur across both material and immaterial issues. Proposals on immaterial issues are associated with subsequent declines in firm valuation while proposals on material issues are associated with subsequent increases in firm value. We show that companies increase performance on immaterial issues because of agency problems, low awareness of the materiality of ESG issues, and attempts to divert attention from poor performance on material issues.

    Keywords: sustainability; activism; Activist Investors; Activist shareholder; corporate social responsibility; corporate accountability; environment; Corporate performance; corporate governance; Corporate Accountability; Corporate Social Responsibility and Impact; Performance; Environmental Sustainability; Corporate Governance; Business and Shareholder Relations; Investment Activism;


    Grewal, Jody, George Serafeim, and Aaron Yoon. "Shareholder Activism on Sustainability Issues." Harvard Business School Working Paper, No. 17-003, July 2016. View Details