2026 03/16–03/20 KOSPI·KOSDAQ Weekly Market Review

KOSPI Weekly Return +3.79% (5,412pt → 5,781pt) | March 16–20, 2026 | Key Themes: Nvidia GTC Shock·AI Demand Explosion vs Middle East Energy Infrastructure Strike·FOMC Warning. Israel's strike on Iran's South Pars gas field and Fed Chair Powell's inflation re-ignition remarks triggered a sharp Thursday sell-off, but on a weekly basis the AI rally overwhelmed the geopolitical shock.

This Week's Market Flow

Monday 3/16 | Semiconductor·Bio-Led Rebound Begins

The KOSPI closed up +1.14% at 5,549.85pt, sparking the start of a rebound. Nasdaq's strength from the previous week's close stoked buying sentiment, with semiconductor heavyweights Samsung Electronics (+1.17%) and SK Hynix (+2.03%) leading the market on the back of foreign net buying. Samsung Biologics surged +4.08%, setting the tone for the bio sector, while automakers including Hyundai Motor (+0.95%) also rose in tandem. However, Dubai crude's continued run at around $105/bbl kept energy cost concerns alive, partially weighing on domestic chemical and refining stocks just as it had capped S&P 500 momentum.

Tuesday 3/17 | Hormuz Reopening Hopes·Foreign Short Covering

The KOSPI added another +1.63% to reach 5,640pt. The prospect of the Strait of Hormuz—at risk of blockade following the Iran-U.S. full-scale conflict—reopening gave a major boost to sentiment as it signaled stabilizing oil prices. Foreign investors who had built up short positions through the prior week began covering in earnest, extending the rebound in semiconductors. Institutional buying joined in toward the close, widening gains, while the KRW/USD exchange rate stabilized slightly to the low 1,490 range, improving conditions for foreign capital inflows.

Wednesday 3/18 | Nvidia GTC AI Shock·KOSPI Sidecar Triggered

The week's pivotal moment. The KOSPI surged +5.04% in a single session to 5,925pt, triggering a KOSPI200 futures buy-side sidecar during the session. The night before (U.S. time), Nvidia GTC 2026 saw CEO Jensen Huang announce that the order backlog for Blackwell Ultra and the Vera Rubin architecture had reached $1 trillion through 2027, sending global optimism on AI demand into explosive territory. Samsung Electronics surged +5.6% in the single session, SK Hynix +4.0%, and SK Square +5.8%. Expectations of HBM and high-bandwidth memory demand benefits translated into valuation expansion across the entire semiconductor supply chain, with power and cooling component stocks tied to AI server infrastructure also posting strong gains.

Thursday 3/19 | Iran Strike·FOMC Shock — Largest Weekly Decline

Before the previous day's enthusiasm could cool, a dual blow of geopolitics and monetary policy struck simultaneously. When Israeli forces struck Iran's South Pars gas field, Iran retaliated by hitting Qatar's LNG export facilities. Brent crude surged intraday to $107.38/bbl (+3.8%), and the market fully digested the fact that the Fed had held rates at 3.50–3.75% at the previous day's FOMC, with Chair Powell publicly warning of "energy-driven inflation re-ignition." U.S. markets closed sharply lower—Dow –768pt (–1.63%), S&P 500 –1.36%, Nasdaq –1.46%. The fallout sent the KOSPI down –2.87%, while the KRW/USD exchange rate breached the psychological resistance level of 1,505 intraday. Samsung Electronics –3.36% and SK Hynix –3.41% gave back a significant portion of the previous day's gains.

Friday 3/20 | Ceasefire Hopes Recover·Oversold Bounce Buying

The KOSPI recovered part of its losses to finish the week up +0.31% at 5,781.20pt. Israeli Prime Minister Benjamin Netanyahu's remarks that "Iran can no longer enrich uranium or manufacture missiles" were interpreted as language consistent with achieving war objectives, easing geopolitical fears somewhat. Follow-through AI optimism from Nvidia GTC supported a technical rebound in semiconductor stocks, and a shift toward dollar weakness adding upward pressure on the Korean won also contributed to a recovery in sentiment. Defense and nuclear power themes—including Doosan Enerbility +3.10%—maintained their geopolitical premium and continued to outperform.

Sector Trends

Outperforming Sectors

AI Semiconductors·Equipment were the week's undisputed star. HBM suppliers Samsung Electronics and SK Hynix maintained positive weekly returns on the back of Nvidia GTC tailwinds, though Thursday's plunge maximized volatility. Semiconductor manufacturing equipment, PCB, and substrate stocks also outperformed on expectations of expanding AI server investment.

Defense·Nuclear Power saw continued expectations for expanded defense budgets as the Iran-Israel conflict prolonged. Nuclear maintenance and export beneficiaries such as KEPCO KPS (RSI near 84) and Doosan Enerbility posted steady gains throughout the week. Construction management stocks like Hanmi Global, benefiting from Middle East infrastructure reconstruction, also came into focus.

Biotech was led by Samsung Biologics, which posted a strong +4.08% gain at the start of the week to set the sector's tone. The rate-hold environment also worked in favor of growth stocks, contributing to a recovery in biotech valuations.

Underperforming Sectors

Airlines·Travel took a direct hit from surging oil prices (into the $107 range). Airline fuel cost burdens translated directly into earnings concerns, and uncertainty over routes due to Hormuz re-blockade risks further weighed on sentiment.

Downstream Chemicals·Refining recorded relative underperformance amid concerns over margin compression from surging input costs. Unlike E&P-related names that benefit from higher oil prices, refining-margin-sensitive sectors lagged.

Utilities saw their relative appeal diminish in a rate-hold, inflation re-ignition environment. However, vertically integrated nuclear power affiliates were an exception, posting unusual strength alongside the defense and nuclear power theme.

Notable Stocks of the Week

Samsung Electronics / SK Hynix — The core of AI semiconductor supply and demand. A GTC-driven surge and Thursday's plunge coexisted, but both posted net gains on a weekly basis. Visibility into HBM4 mass production timelines is the next catalyst.

SK Square — Posted the largest weekly gain among GTC beneficiaries on expectations of a revaluation of its SK Hynix stake and narrowing of the AI investment portfolio discount. Maximum leverage effect among GTC winners.

Doosan Enerbility — Steady weekly outperformer on nuclear and defense tailwinds amid Middle East risks from the Iran strike. Export momentum continues as a key supplier of critical nuclear components.

KEPCO KPS — Entered RSI overbought territory on its monopoly in nuclear maintenance and expectations of overseas export contracts. A buy-on-dip strategy after a short-term correction remains valid.

Hanmi Global — No. 1 CM stock benefiting from Middle East and public infrastructure reconstruction. A breakout above the 52-week high would confirm a trend reversal.

Next Week Outlook and Key Variables

① Iran-U.S. Ceasefire Negotiation Progress The most important variable. If Netanyahu's remarks develop into genuine negotiation signals, a sharp drop in oil prices and a KOSPI semiconductor re-rally would be expected. Conversely, further Iranian retaliation or a Hormuz re-blockade opens the possibility of KOSPI breaking below 5,600pt.

② Oil Price Direction If Brent crude remains above $107, Powell's inflation warning gains credibility and rate-cut expectations retreat, creating headwinds for growth stocks. A return to stability below $100 would restart broad market re-rating.

③ KRW/USD Exchange Rate Breaking above 1,505 has increased the FX hedging cost burden for foreign investors. Unless the exchange rate stabilizes below the 1,490 range, a return to net foreign buying will be limited. Watch the dollar index and Fed commentary.

④ Interpretation of the FOMC Dot Plot The market is re-reading how Powell's energy inflation remarks were reflected in the March dot plot. If in-year rate cuts are revised down to two or fewer, valuation de-rating pressure will increase.

⑤ Return of Foreign Net Buying Foreign net selling resumed after Thursday. A meaningful return to net buying can only be expected if both dollar strength and surging oil prices ease simultaneously. Without a return of foreign flows, institutions alone will struggle to defend the market.

⑥ Post-Nvidia GTC Supply Contract Announcements If domestic HBM, packaging, and substrate companies follow up with supply contract announcements, individual stock surge events could occur. The market is focused on the outcome of Samsung Electronics' HBM4 Nvidia supply negotiations.

Investor Action Guidelines

Short-Term (1 week): Monitor oil prices and Iran-related headlines in real time. If Brent crude holds above $105, refrain from new buys in semiconductors and biotech; if it breaks below $100, treat that as a signal to increase exposure. Whether KOSPI holds 5,700pt is the key technical inflection point.

Medium-Term (2–4 weeks): The AI infrastructure investment cycle has been structurally reinforced post-GTC. Short-term volatility stems from geopolitical risk, so a phased buying strategy on sharp declines in Samsung Electronics and SK Hynix remains valid. As a significant portion of the geopolitical premium is already priced into defense and nuclear power stocks, wait for a pullback before initiating new positions.

Risk Management: If KRW/USD breaks above 1,510, maintain dollar asset allocation within the portfolio and consider reducing KRW asset exposure. If you have already trimmed airlines and chemical stocks in preparation for a Hormuz re-blockade scenario, no additional action is necessary. For GTC beneficiaries with RSI above 80 in overbought territory (KEPCO KPS, CS Bearing, etc.), set re-entry levels after taking short-term profits.