Why Is KOSPI Rising Despite a Bank of Korea Rate Hike? Samsung and SK Hynix Lead AI Rally

 

On the morning of August 27, the Bank of Korea raised its benchmark rate by 25 basis points to 3.00%, the first back-to-back hike since January 2023. Conventional logic says a tightening central bank compresses equity valuations. Instead the KOSPI opened at 6,996.12, up 187.91 points or 2.76%, approaching 7,000 for the first time in seven sessions, and still held gains of roughly 1.93% around 11:20 a.m.

 

The explanation is not in the rate statement. It is in what happened after the U.S. close the previous evening. Nvidia's quarterly results not only beat on revenue but explicitly flagged rising memory costs as a drag on its own gross margin. For the world's two largest memory suppliers, that sentence could hardly be more direct: profit is migrating from the accelerator vendor to the memory vendors. Samsung Electronics and SK Hynix opened up 3.25% and 5.45% respectively, with foreign investors buying roughly 200 billion won.

 

The relationship between the two events is what deserves unpacking. The Bank of Korea's stated reason for tightening was precisely the income growth and inflationary pressure generated by the semiconductor boom. The cause of the hike and the cause of the rally are the same thing. When tightening originates in an earnings cycle rather than an external shock, an equity market can rationally price the cause and ignore the policy.

 

 

 

On the decision itself, the Monetary Policy Board approved the hike six votes to one out of seven members, returning the base rate to the 3% range for the first time since February 2025. Governor Shin Hyun-song characterised the move as preemptive while stressing that the rate path is not predetermined and that each decision remains live, citing a dot plot in which a majority of members project 3.25% in six months.

 

On the data, second-quarter real GDP grew 0.6% quarter on quarter, three times the BOK's May forecast of 0.2%, following 1.8% in the first quarter. On that basis the bank raised its 2026 growth forecast to 3.3% from 2.6% in May, and that 2.6% had itself already been revised up from 2%.

 

On inflation, July core inflation climbed to 2.6%, the highest since December 2023, while headline cooled slightly to 2.8% after rising every month since February. Seoul housing prices rose 2.5% month on month in June, the largest monthly gain in five years.

 

On the external catalyst, Nvidia's fiscal second-quarter revenue reached $96.2 billion, up 106% year over year, with third-quarter guidance of $108.0 billion plus or minus 2%, the first time it has pointed past $100 billion in a quarter. The company also expects fourth-quarter gross margin to fall to 71% to 72%, partly because of memory prices.

 

 

 

In form this was a hawkish decision. Six of seven members supported the hike with one dissent. Consecutive hikes are uncommon in the Bank of Korea's history, with the last instance dating to January 2023, at the tail of seven straight increases that began in April 2022.

 

July's hike was the first in three and a half years, lifting the rate from 2.50% to 2.75%. The contrast is instructive: the KOSPI fell more than 6% that day, with Samsung Electronics and SK Hynix tracking losses in U.S. chip stocks. Identical policy action, six weeks apart, opposite market reaction. That comparison alone demonstrates that the rate decision is not what sets direction here.

 

 

Most headlines fixate on the rate number, but for equity investors the growth forecast matters more. Moving from 2% to 2.6% to 3.3%, the Bank of Korea has revised its 2026 growth projection upward twice within months, a cumulative 1.3 percentage points. For a mature economy that is an unusually large revision.

 

The stated reasoning was equally clear: both exports and domestic demand are expected to show strong growth, supported by spillover effects from the semiconductor sector. The central bank has formally acknowledged in an official document that this cycle's growth and inflation originate in chips. That is a positive input for equities, because it validates the strength of the earnings cycle through an official channel, and the earnings cycle is the numerator in any valuation.

 

Worth noting is that the BOK had previously flagged that large performance bonuses paid by some major IT-sector companies could translate into broader wage increases and upward inflation pressure. That transmission path links the chip industry's profitability directly to national inflation and is central to understanding this hike.

 

 

 

Direction was set before the open by a U.S. earnings report. Per the results release, Nvidia's fiscal second-quarter revenue reached $96.2 billion, up 18% sequentially and 106% year over year, with Data Center revenue of $89.0 billion up 117% and accounting for roughly 93% of the total. GAAP and non-GAAP gross margins were both 75.0%, and non-GAAP earnings came to $2.22 per share. Third-quarter guidance is $108.0 billion plus or minus 2% with gross margin of 74.0% plus or minus 50 basis points, assuming no Data Center compute revenue from China.

 

What mattered to Korea were two statements on the call. Per CNBC, the company expects gross margin to bottom in the fiscal fourth quarter at 71% to 72%, partly because of memory prices, with CFO Colette Kress saying memory scarcity today is being driven in large part by the AI buildout itself. Per Kiplinger's live coverage, CEO Jensen Huang said of the roughly 70% fiscal 2028 growth outlook that the company has supply for that level while demand runs much higher.

 

Read together, the conclusion strongly favours memory suppliers. The world's most important accelerator vendor publicly conceded that its own gross margin will fall three to four percentage points because of memory costs, and that the scarcity persists into the next fiscal year. Margin does not evaporate. It transfers along the supply chain. Samsung Electronics and SK Hynix are where those three to four points land.

 

 

The open confirmed that logic. At 9:05 a.m., Samsung Electronics traded at 270,000 won, up 8,500 won or 3.25%, while SK Hynix was at 1.78 million won, up 92,000 won or 5.45%. Foreign investors, hesitant a day earlier, returned as buyers with net purchases near 200 billion won. By roughly 11:20 a.m. the index had pared its gain to about 1.93%, with Samsung and SK Hynix holding around 2.29% and 3.44%.

 

That fade deserves recording on its own. Giving back roughly a third of a 2.76% opening gain within a couple of hours shows the market did not simply ignore the hike; it reintroduced the rate variable once the initial enthusiasm passed. Opening strong and drifting while holding most of the advance reflects genuine price discovery better than a straight-line rally would.

 

 

 

The same 25 basis points can produce opposite reactions depending on why they were delivered. If a central bank is forced to tighten against imported inflation or currency depreciation, the hike signals stress in the real economy and both numerator and denominator deteriorate. If it tightens because growth ran ahead of forecast and corporate profitability is lifting wages and prices, the hike is a confirmation of earnings strength, and improvement in the numerator can offset or exceed the rise in the denominator.

 

This was plainly the latter. In the same document the Bank of Korea raised its growth forecast by 0.7 percentage points and wrote semiconductor spillover into its reasoning. For an index this concentrated in semiconductors, that is a policy statement readable as constructive.

 

The logic has a boundary, of course. Above some level of rates the denominator effect begins to dominate, particularly for growth names already carrying high multiples. How far 3.00% sits from that threshold is something nobody can answer reliably today.

 

 

The second transmission channel gets overlooked. With the base rate at 3.00% against a U.S. federal funds upper bound of 3.75%, the Korea-U.S. differential narrowed to 0.75 percentage points from 1, which supports the won.

 

For foreign investors that is a real return factor. Dollar returns on Korean equities combine price movement with currency movement, and improved expectations for the won convert the same price gain into a higher dollar return. That helps explain the day's foreign buying. By contrast, when the KOSPI rose nearly 6% on August 20, the won weakened, a combination that was considerably less attractive for offshore money.

 

 

 

To understand how one American earnings report can lift an entire national market close to 3%, the index structure has to be confronted. Samsung Electronics and SK Hynix together carry an extremely high combined weight in the KOSPI, and SK Hynix briefly became Korea's largest listed company by market value at mid-year. When two names dominate, the index's risk characteristic is no longer the Korean economy. It is global AI memory demand.

 

The past two months have tested that repeatedly. In July the KOSPI fell more than 22%, entering bear market territory. On August 20, after SK Hynix announced a 40 trillion won buyback, the index rose 5.89% to 6,852.58 in a single session, and the Korea Exchange triggered a buy-side sidecar suspending program trading for five minutes as KOSPI 200 futures rose 5%. Earlier this week, ahead of Nvidia, the index fell 2.7% in one session.

 

Even through those swings, the KOSPI is up more than 55% in 2026, following a 76% gain in 2025 that was its strongest annual performance since 1999.

 

 

A major national equity index falling 22% in a month and rising nearly 6% in a day does not exhibit index-like volatility. It behaves like a high-beta single stock.

 

The practical implication is that treating the KOSPI as a diversification tool no longer holds. Passive exposure to it is effectively a concentrated position in AI memory. Understanding its direction depends less on Korean macro data than on high-bandwidth memory pricing and order books. That is also why, with SK Hynix roughly 45% below its June high, mapping its specific technical levels is more useful than debating index points.

 

 

For investors tracking this theme outside Seoul hours, the related equity contracts listed on MEXC provide continuous quotes, with the usual caveat that basis against Korea Exchange execution prices exists.

 

 

The rate path is the first variable. The governor indicated a gradual pace of increases over the next six months, and the dot plot shows a majority projecting 3.25% in six months, meaning at least one more hike sits inside expectations. If rates keep rising while the AI narrative wobbles, the denominator effect ignored today returns immediately.

 

The durability of memory pricing is the second and most consequential. Nvidia expects gross margin to bottom in the fiscal fourth quarter before stabilising in fiscal 2028, with plans to raise prices. Implicit in that is management's view that memory cost pressure eases within a year. If that holds, the pricing-power window memory suppliers currently enjoy has a time limit. Samsung has already introduced next-generation high-bandwidth memory, and second-source qualification at scale would move the industry price level directly.

 

Currency and inflation form the third. Headline inflation eased slightly in July but had risen every month since the U.S. and Iran conflict began in February, with energy the main driver. If oil moves higher again, the Bank of Korea could be forced from preemptive tightening into reactive tightening, at which point the cause of the hike shifts from profitability to costs and the market's interpretive frame changes entirely.

 

Finally there is valuation. The KOSPI is up more than 55% this year after 76% last year, having opened 2026 at a record above 4,300. On that base, any doubt about the AI capital expenditure cycle gets amplified. Nvidia's own free cash flow fell to $21.3 billion from $48.6 billion in the prior quarter while it raised roughly $24.9 billion in new debt, and changes in cash conversion and financing structure of that kind are worth tracking over time.

 

 

What deserves recording about this session is not how far the KOSPI rose but that the market answered, in prices, a long-contested question: whether tightening is necessarily bearish for equities. The answer depends on why. When a central bank tightens because income generated by the semiconductor industry is pushing inflation higher, the hike is official endorsement of an earnings cycle rather than a withdrawal of liquidity. The Bank of Korea raising its 2026 growth forecast from 2.6% to 3.3% in the same document carries far more information for equity investors than 25 basis points does.

 

The likeliest misreading is attributing the entire rally to Nvidia's results. That attribution is incomplete. The actual mechanism was two pieces of information arriving simultaneously: external confirmation of demand, and domestic confirmation that this demand has grown strong enough to change a country's monetary policy. With only the first, the move would have looked like ordinary sector follow-through. With only the second, the market would probably have fallen as it did in July. Their coincidence produced this unusual combination.

 

The second underrated detail sits in those three to four percentage points of Nvidia's margin guidance. The company expects fourth-quarter gross margin at 71% to 72% and attributed part of that to memory prices. In earnings language that is remarkably blunt. A company occupying the strongest bargaining position in the chain publicly conceding that its margin is being eroded by upstream costs amounts to third-party certification of memory suppliers' pricing power. That information is worth more than any sell-side note because it comes from the buyer.

 

From a risk management standpoint, three data series outrank the index level over coming weeks. First, high-bandwidth memory contract pricing and quarterly order visibility, which determine how long the profit transfer lasts. Second, the vote split at the Bank of Korea's next two meetings, since a move from six to one toward five to two or four to three would signal rising internal concern about the cost of tightening. Third, the direction of sustained foreign flows in the KOSPI, because with the differential now at 0.75 percentage points, currency has become a heavier weight in offshore decision-making and flow direction reveals medium-term positioning better than daily moves.

 

For cross-asset investors, this offers a methodological reminder. When two stocks dominate an index's variance, explaining it through a macro framework will fail consistently. Today's correct explanatory path runs from a U.S. earnings report, through memory pricing, to a Korean index, and only then reaches the domestic central bank. That bottom-up sequence has now appeared in several markets across this AI capital expenditure cycle, and the Nasdaq's dependence on a handful of companies belongs to the same structural category. Identifying which link in the supply chain holds the real driver matters more than forecasting the direction of rates. All of the above rests on published policy statements, filings and market data and is not a definitive conclusion about future direction.

 

 

 

The Monetary Policy Board raised the benchmark rate by 25 basis points to 3.00% on August 27, a second consecutive increase following July's hike and the first back-to-back tightening since January 2023. The decision passed six votes to one among seven members. The level is the highest since January 2025 and returns the base rate to the 3% range after roughly a year and a half.

 

 

Because the reason for the hike and the reason for the rally are the same. The Bank of Korea named semiconductor spillover effects as the main source of growth and inflation and raised its 2026 growth forecast from 2.6% to 3.3%. For equity investors that amounts to official confirmation of the earnings cycle. At the same time, Nvidia's results the previous evening beat expectations and flagged rising memory costs as a drag on its own margin, which is a direct positive for memory suppliers.

 

 

Because Samsung Electronics and SK Hynix are the world's principal memory suppliers and the KOSPI is heavily concentrated in those two names. Nvidia's second-quarter revenue of $96.2 billion, up 106% year over year, and third-quarter guidance of $108 billion confirmed the strength of AI demand. More importantly, the company expects fourth-quarter gross margin to fall to 71% to 72% partly because of memory prices, which means profit is migrating from the accelerator vendor to the memory vendors.

 

 

The KOSPI opened at 6,996.12, up 187.91 points or 2.76%, approaching 7,000 for the first time in seven sessions. At 9:05 a.m., Samsung Electronics traded at 270,000 won, up 3.25%, and SK Hynix at 1.78 million won, up 5.45%. Foreign investors bought roughly 200 billion won net. By around 11:20 a.m. the index had pared to about 1.93%, indicating the market reintroduced the rate variable once the initial enthusiasm passed.

 

 

Governor Shin Hyun-song indicated a gradual pace of increases over the next six months, with the dot plot showing a majority of members projecting 3.25% in six months, while stressing that the path is not predetermined and every decision stays live. July core inflation at 2.6% was the highest since December 2023, and Seoul housing prices rose 2.5% month on month in June, the largest monthly gain in five years, both supporting further tightening.

 

 

With the base rate at 3.00%, the Korea-U.S. differential narrowed to 0.75 percentage points from 1, which supports the won. For foreign investors, dollar returns on Korean equities combine price and currency, so improved expectations for the won lift the dollar return on any given price gain. That partly explains the shift to net foreign buying that session and is one reason the hike was not purely negative in this context.

 

 

Three. On rates, at least one more hike sits inside expectations, and any wobble in the AI narrative brings the ignored denominator effect straight back. On memory pricing, Nvidia expects margins to stabilise next fiscal year and plans to raise prices, implying cost pressure eases within a year and the suppliers' pricing window has a time limit. On valuation, the KOSPI is up more than 55% this year after 76% last year, and July's 22% single-month decline shows how quickly that can reverse.

 

 

Structurally, no longer. Samsung Electronics and SK Hynix carry extremely high index weight, and SK Hynix briefly became Korea's largest listed company by market value at mid-year. Passive exposure to the index is effectively a concentrated AI memory position. A 22% single-month decline in July and a 5.89% single-day gain on August 20 that triggered a buy-side sidecar describe a high-beta single stock rather than a diversified national index.

 

 

This article is provided for information and market analysis purposes only and does not constitute investment advice, financial advice, legal advice, tax advice, or any recommendation to transact. Prices of equities, crypto assets, currencies and other related financial instruments can move sharply, and the market discussed here has repeatedly produced monthly moves above 20% and daily moves near 6% in recent weeks. None of the policy statements, economic data, earnings figures, intraday quotes or market reactions referenced here can guarantee future outcomes, and intraday data is captured at specific moments that may differ materially from closing levels. The policy path judgments, scenarios and supply-chain profit transfer logic described are forward-looking and may not be realised, with the official disclosures of the Bank of Korea, the relevant listed companies and exchanges taking precedence. Investors should reach independent conclusions based on their own financial circumstances, investment objectives, experience and risk tolerance, consulting a qualified professional where appropriate. The MEXC Crypto Pulse team accepts no liability for any direct or indirect loss arising from the use of, or reliance on, the information contained in this article.

 

 

James Mitchell specializes in technical analysis, market trends, and trading strategies for both Bitcoin and altcoins. Based in London, he has over 10 years of experience in financial markets. Before joining MEXC Learn, James worked as a senior analyst at a leading European investment firm, where he developed expertise in risk management and quantitative trading. His transition to cryptocurrency markets began in 2017, and he has since become recognized for his data-driven approach. He holds a Master's degree in Financial Economics from the London School of Economics. His analytical approach combines traditional technical analysis with on-chain metrics to provide readers with actionable insights.

 

His areas of expertise span technical analysis, market trends and cycles, trading strategies, Bitcoin and altcoin analysis, and risk management.

 

 

 

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