Research seminar: Yen-Cheng Chang (National Taiwan University)

We would like to invite you to a research seminar by Yen-Cheng Chang, Professor of Finance at National Taiwan University.

Title: *When Bad News Travels Faster: Evidence from Disclosure Integration and Post-Earnings Announcement Drift*

Authors: Yen-Cheng Chang (NTU), Bokyung Park (Sookmyung Women’s University), Yu-Siang Su (NCNU, NTU), Kevin Tseng (Chinese University of Hong Kong), and Tzu-Wen Yu (NTU)

Abstract: We study how information integration frictions shape retail investors’ responses to earnings news and drive post-earnings announcement drift (PEAD). Using the staggered rollout of the Electronic Data Gathering, Analysis, and Retrieval (EDGAR) system as our identification setting, we provide direct, investor-level evidence that reduced disclosure processing costs mitigate PEAD, with the attenuation concentrated among bad-news earnings announcements. We develop a parsimonious slow-diffusion model that clarifies how disclosure acquisition and integration map into PEAD and trading volume. Guided by this framework, mechanism tests point to a retail investor integration channel: retail trading around earnings announcements declines after EDGAR inclusion, consistent with more uniform integration. In particular, contrarian retail buying after bad news falls sharply, helping to explain why PEAD attenuates most on the short leg. We further exploit the eXtensible Business Reporting Language (XBRL) mandate and find cross-sectional evidence consistent with retail investors benefiting from XBRL through a different integration channel that operates on structured disclosure data.

The seminar will take place on *Thursday*, June 11, 2026, in Room 206 at 13:00.

A preliminary version of the paper is available here.

If you need a discussion slot with Prof. Chang, please write to Prof. Jozef Baruník, and he will try to find a suitable time.

The list of all research seminars at IES (past and forthcoming) is available at: https://ies.fsv.cuni.cz/en/research/research-seminars