Rollercoaster Trading as ETF Flows Amplify Volatility
KOSPI swung wildly within a single session, rising as much as 1.6-1.8% to touch 8,933 points before plunging to 8,500 within roughly 30 minutes. KOSDAQ also weakened close to 3%, trading around the 108-point range. Hosts noted that volatility tends to cluster in the first 30 minutes after the market opens, since thin volume during the pre-market and early regular session leaves prices vulnerable to distortion from one-sided flows.
A structural driver behind the volatility is the rapid growth of passive ETFs. Domestic ETF assets have surpassed 500 trillion won, meaning at least 10% of the roughly 7,000 trillion won KOSPI market cap now moves in lockstep with ETF flows. The problem, panelists explained, is that the trigger needed to move this massive pool is comparatively tiny — even modest foreign or retail selling can set off outsized reactions across the entire 500 trillion won pool, a case of the tail wagging the dog.
Foreign investors net sold more than 5 trillion won on the KOSPI at one point during the session. The primary driver was profit-taking and rebalancing in recently surging names — stocks like Samsung Electro-Mechanics and LG Innotek, which had posted consecutive upper-limit gains over the past week, bore the brunt of the selling. Samsung Electro-Mechanics plunged about 12%, compounded by month-end ETF rebalancing within three business days, while LG Innotek fell nearly 20%.
A secondary factor cited for foreign selling was the need to raise cash ahead of the SpaceX IPO. SpaceX filed official IPO paperwork on May 20, with an institutional roadshow ahead of pricing on June 11 and a Nasdaq listing on June 12. Because the listing structure differs from Korea's, institutions reportedly need to have subscription funds ready by the 11th — a date that also coincides with quadruple witching in futures and options, adding to the volatility.
Panelists offered guidance for beginner investors: a 20%-plus intraday loss within just three to four hours is rarely justified by fundamentals, so if the exit window was missed, it's often better to stay calm and watch rather than panic-sell. They also stressed that investing is not a task to rush through — rather than deploying a full day's planned purchase at once, spreading it out and pacing decisions is a healthier habit.
The panel concluded that market swings shouldn't be judged as simply right or wrong but adapted to as a structural feature of today's market. Notably, on days like this, stocks that hold up better than the index or actively resist the decline tend to be the ones that jump first when the market turns higher — a signal worth watching.