The primary objective of this research is to measure the information asymmetry before, during, and after earnings announcements and how it relates to the drift in post-earnings announcements over an extended period. The study uses the bid-ask spread as an information asymmetry proxy and employs a market model to assess daily data on Indonesia’s equity market before, during, and after the earnings announcement. Data were analyzed using the t test and least squares regression. The study provides empirical evidence showing that the bid-ask spread increases significantly before the earnings announcement, indicating information uncertainties between sellers and buyers. The findings show that the market reacts to accounting information indicated by a significantly reduced bid-ask spread soon after the market digests the information, following the concept of semi-strong market efficiency. The study shows a cumulative abnormal return and bid-ask spread strongly correlated a few days following earnings. However, the analysis found no long-term association between bid-ask spread and post-earnings announcement drift. The study found that stock market sellers and buyers use accounting data to set prices and that earnings releases reduce the bid-ask difference. The study suggests that the market regulator supports timely disclosure of this information.
Nainggolan et al. (2025) studied this question.