"I thought there was an error because the stock prices moved suddenly on the first day of the aftermarket."
After 4 p.m. on September 14, the Korea Exchange (KRX) opened its aftermarket for the first time. As I turned on the mobile trading system (MTS) and checked various stocks, I noticed unusual movements that are rarely seen during regular trading hours. Some stocks had sporadic bid prices, and even with low trading volumes, stock prices fluctuated rapidly. Initially, I suspected a system error, but it turned out that the low liquidity of the stocks with fewer participants was the cause.
On this day, the aftermarket saw significant volatility, particularly among small-cap stocks. By 7:15 p.m., the number of volatility interruption (VI) triggers reached 1,591, nearly four times the level seen during regular trading hours. Stocks with low trading volumes experienced substantial price swings, with some showing fluctuations of around 20-30% during the session.
In contrast, actively traded stocks did not show significant differences from regular trading. A 32-year-old investor, identified only as Lee, participated in the KRX aftermarket for the first time. He chose Bit & Electronics, which ranked high in trading volume that day.
Bit & Electronics was not a stock previously traded on the alternative exchange NextTrade (NXT). When Lee placed a buy order after 4 p.m., it was executed immediately. He remarked, "It was fascinating to be able to buy and sell stocks that couldn't be traded on NXT even after the market closed. It felt quite similar to trading during regular hours. I think I will keep an eye on stock movements after regular trading from now on."
After all trading concluded on the first day, small-cap stocks dominated the trading volume rankings. Bit & Electronics recorded over 80.46 million shares traded on the KOSDAQ, followed by Dream Security with 38.35 million shares and Kosnine with 30.53 million shares. Exgate and Samik Pharmaceutical also saw 16.67 million and 16.13 million shares traded, respectively. Bit & Electronics closed at 4,355 won, up 12.53% from the previous trading day, while Sands Lab rose 29.95% to 7,160 won.
On the KOSPI, Gwangjeon topped the trading volume with 28.98 million shares, closing at 10,270 won, a 30.00% increase from the previous day. Samsung Electronics traded 17.76 million shares, while SM Vexcel and Heung-A Shipping saw 10.68 million and 10.60 million shares traded, respectively. Samsung Electronics closed down 4.24% at 248,500 won.
Notably, stocks like Bit & Electronics, which ranked high in trading volume, were not available for trading on the previous NXT platform, highlighting the impact of the KRX aftermarket's introduction. While only about 600 stocks were traded on the NXT aftermarket, the KRX allows trading of most KOSPI and KOSDAQ listed stocks, excluding those under investment warnings or management. This means that small-cap stocks, which were virtually impossible to trade after regular hours, can now be traded in real-time until 8 p.m.
The trading method has also changed. The previous after-hours single-price market, which operated from 4 p.m. to 6 p.m., has been abolished, and a continuous trading method similar to regular hours is now in place from 4 p.m. to 8 p.m. Orders are executed in real-time when buy and sell prices match. However, market orders are not allowed, and ETFs and ETNs are excluded from aftermarket trading.
Investors should also be aware of certain aspects. Samsung Securities has advised that unexecuted orders sent to the KRX regular market before the aftermarket will automatically have their margins released after the regular market closes, requiring investors to place new orders in the aftermarket. In contrast, NXT orders will remain valid until the aftermarket. During the overlapping hours of 4 p.m. to 8 p.m. when both KRX and NXT operate, best execution obligations will also apply.
The landscape of the Korean stock market, which previously ended at 3:30 p.m., has changed with the addition of KRX's evening trading. Investors can now trade a wider range of stocks in real-time even after regular hours. For those who traded directly on the first day, the most noticeable change was the increase in the number of tradable stocks rather than the order method itself. However, with significant price fluctuations observed in some low-liquidity stocks from day one, managing liquidity and volatility during the extended trading hours will likely become a new challenge.
* This article has been translated by AI.
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