Widened Price-Limits and Efficiency of Price Discovery over the Course of a Trading Day Open Access

Korea Exchange has widen daily price limits from ±15% to ±30% of previous trading day’s closing price since June 15, 2015. In this paper, we examine how the event of widening price limits affect price discovery process over the course of trading day. In order to conduct this investigation, we compare price efficiency during such price discovery before and after the event. The changes that has occurred after the event can be summarized as follows: First, an analysis on full-sample indicates that price efficiency is maintained over the course of a trading, while it is aggravated temporary in two early intervals. Second, an analysis on sub-samples sorted by market capitalization, shares outstanding, or share price indicates that temporary aggravation of price efficiency in some mid-intervals is observed for shares outstanding lower group and share price top group. Overall, our results suggest that evidence supporting information hypothesis is found for the whole process of price discovery over the course of a trading day, though evidence supporting over-reaction hypothesis is found in some intervals or some types of stocks.