Hieu Pham

Type of the article: Research Article

Abstract
Voluntary disclosure theory predicts that managers delay bad-news disclosure and accelerate good-news disclosure when firm-specific uncertainty rises. However, this prediction may not hold in low-trust frontier markets. This study aims to determine whether lagged idiosyncratic volatility changes the timing of good- and bad-news voluntary disclosure in Vietnam and whether environmental, social, and governance performance, analyst coverage, and state ownership moderate that relation. The study uses hand-collected voluntary disclosures from 210 Vietnamese non-financial listed firms over 2018–2024 and estimates probit models with firm and year-month fixed effects on 5,122 firm-month observations. The results show a reversal of the developed-market pattern. A one-standard-deviation increase in lagged idiosyncratic volatility raises the probability of bad-news disclosure by about 12 percentage points and lowers the probability of good-news disclosure by more than 17 percentage points. Higher environmental, social, and governance performance does not weaken this asymmetry and instead amplifies it; analyst coverage provides no mitigating effect, and the reversal is stronger in state-owned enterprises. Robustness tests using two-way clustering, paired cluster bootstrap, random subsample splits, and placebo volatility confirm the pattern. The findings indicate that disclosure incentives under uncertainty depend on institutional trust and ownership structure, so governance mechanisms effective in mature markets cannot be assumed to operate similarly in Vietnam.

Acknowledgment(s)
This research was funded by Ho Chi Minh City University of Technology and Engineering (HCMUTE), Vietnam, under grant number T2025-143.