Korea Exchange sees erratic trading in first after-hours session

South Korea’s stock exchange opened its doors after dark for the first time on September 14, and the results were, well, chaotic. The Korea Exchange’s debut after-hours session drew roughly 1.8 trillion won (about $1.33 billion) in turnover, a respectable showing that also happened to trigger 1,637 volatility interruption halts. For context, a normal daytime session sees around 400.

The four-hour window, running from 4 p.m. to 8 p.m. local time, was designed to let Korean investors react to global market developments outside traditional hours.

Retail investors ran the show

The most striking detail from the inaugural session: retail investors accounted for 93% of the total turnover. Foreign investors contributed just 3.9%, and institutional participation was essentially a rounding error.

The session saw 72.24 million shares change hands across 2,501 stocks, covering over 95% of listed KOSPI and Kosdaq names. That breadth is a significant expansion compared to the previous Nextrade system, which offered far fewer eligible securities.

Some of the price action was dramatic. Shares of Hanwha Galleria surged 14.6% before pulling back. The 1,637 volatility interruption activations represent more than four times the typical daytime frequency.

Why KRX built this in the first place

The after-hours session is KRX’s answer to a competitive problem. Major global exchanges like Nasdaq and the NYSE have offered extended-hours trading for years, allowing investors worldwide to trade around US market catalysts in near-real time. South Korea’s traditional trading hours left domestic investors unable to respond to overnight developments until the next morning’s bell.

The 1.8 trillion won in first-session volume, roughly 7% of average regular-hours turnover, suggests genuine demand exists.

The liquidity question looms large

Analysts have flagged the liquidity gap as the central challenge for KRX’s extended session going forward. Institutional investors stayed on the sidelines during the debut, and many institutional mandates restrict trading to core hours. Algorithmic trading firms, which supply much of the liquidity on global exchanges during extended hours, also need time to calibrate strategies for a brand-new session.

The volatility interruption mechanisms clearly earned their keep during the first session, but if after-hours trading continues to trigger halts at four times the normal rate, KRX may face pressure to introduce additional safeguards or adjust the rules around market-making obligations during extended hours.

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