[Analysis] Causes of KOSPI Plunge: Semiconductor Sell-off and Foreign Flight

On June 5, 2026, the South Korean stock market faced intense selling pressure, leading to a panic-selling environment. The KOSPI index plunged over 6% early in the session, shocking the market and triggering a sell sidecar that temporarily halted program trading. This severe downturn is a complex result of fundamental concerns in the global semiconductor sector combined with record capital outflows by foreign investors.

Global Headwinds and the Semiconductor Collapse

The most direct cause of the index's decline originated from the sluggishness of US tech stocks, specifically the Broadcom earnings shock. Overnight, Broadcom released poor results that fell short of the market's high expectations, along with a forecast of slowing artificial intelligence (AI) semiconductor revenue, abruptly cooling investor sentiment across the global technology sector.

• As the standards for verifying the earnings of key companies that have led the global AI rally become stricter, widespread concerns over valuation overestimation are materializing.
• This bearish trend in US semiconductor stocks acted as a direct downward pressure on domestic chip heavyweights Samsung Electronics and SK Hynix, pulling down the entire index forcefully.

Record Foreign Capital Flight and Shrinking Market Sentiment

The underlying reason making KOSPI's drop particularly steep is a collapsed supply-demand balance. The aggressive departure of foreign investors is highly alarming. As of June 5, foreigners have maintained a net selling position for 20 consecutive trading days, spearheading the KOSPI's decline. This marks the longest streak of net selling recorded in the past six years.

This massive sell-off by foreigners transcends simple short-term profit-taking. It is interpreted as a structural capital withdrawal reflecting conservative views on global macroeconomic uncertainties and fears of the semiconductor industry peaking out. With domestic retail and institutional buying falling short of absorbing the deluge of supply, volatility has been maximized.

Implications for Investors and Strategic Response

Currently, the domestic stock market exhibits a vulnerable state, heavily swayed by global supply-demand volatility and investor sentiment rather than company-specific fundamentals. For the time being, the stabilization of US tech stock prices and whether foreign investors shift to net buying will be the core triggers determining KOSPI's rebound.

Therefore, investors should be wary of indiscriminately buying the dip due to the excessive drop. A cautious attitude is required, conservatively approaching stocks with solid fundamentals only after confirming a clear bottoming and rebounding trend in major global tech indicators and foreign supply-demand data.